Rolled back to Chrome 137 for very important personal reasons; need help w/ profiles & backup data!

PRELIMINARY NOTE: This question pertains to matters of sign-in/sync, extension management, & using Chrome, so I put it under the "other questions & issues category".

Now, please read this post very, very, very slowly & carefully, because it's extremely complex. Why? Well, I want to make sure that absolutely no information is mistakenly omitted or made unclear in any way.

(sighs) Or, if you really must prefer to read a streamlined version of this post, see it here. I sincerely doubt that it will be as effective as the full thing, though.

PART ONE: No Chrome With Manifest 3!

All right, to begin with: Google Chrome version 138 positively stinks, sucks, & eats nuts. This is because it runs on Manifest 3, & with it, I can no longer (re)enable certain extensions that worked perfectly fine up until then--& the majority of which contain very important saved data pertaining to all sorts of projects, pastimes, & purposes of mine. (Some of this data goes back a few years!) So, in order to restore Chrome's previous functionalities, I rolled back Chrome back to the last version with Manifest 2 (137), turned off automatic Google updates in Windows Services, & copied & pasted my original User Data folder that I have backed up on Flash drive (& also elsewhere on my hard drive).

Incidentally, this is a complete list of all of the steps I followed to carry out this entire process, graciously provided to me by Google Search:
how to prevent data corruption when reinstalling a previous version of google chrome

I'm undoubtedly going to be jumped on for doing the things recently described, BUT I DO NOT CARE. My extensions & their saved data are FAR too important for me to lose access to.

So, with these things out of the way, I shall now move on to...

PART TWO: That Time When Chrome Updates Messed Up My Profiles

Before all this happened, Chrome first screwed me over when it did an update, & messed up my default profile by putting the majority of its contents in this strange folder called 'Profile 1' in Appdata. Having no idea where all my data had gone & what the deuce had happened, I feared that everything had been deleted forever, & was thus totally inconsolable to the point of actual tears. Hoping that someone might be able to help me, I posted about this issue on Reddit, & was luckily able to get the perfect solution from them! ^_^ You can read all the details about it here:

So, once I found out where all of my data had been moved to, my "default" profile became "Profile 1" instead, & that was how I was able to access all of my extensions, bookmarks, history, other data, etc., from that point onward.

Now, let us return to the subject of my rollback installation of Chrome 137. When I copied & pasted my original User Data folder that I have backed up on Flash drive (& also elsewhere on my hard drive)...Chrome would show up for a split-second, then crash. It took me several attempts at failing to open Chrome that got me to find out what the problem was: apparently, there was a faulty "web data" file in every profile folder that got Chrome confused, thus prompting it to move all of the non-faulty data to a new third profile (named "Profile 2").

And the reason for all that, was because (as per the steps outlined in the document linked above) I made the mistakes of A) leaving the Internet connected while I was installing Chrome 137, thus allowing it to be automatically updated right in the process of trying to restore the older version & all of its backed-up info; & B) copying & pasting my backed-up User Data folder into the Chrome Appdata folder right in the middle of this faulty installation! So, after uninstalling & reinstalling Chrome 137 with Internet disconnected, copying & pasting the backed-up User Data folder into the newly-created Chrome Appdata folder, disabling automatic updates, & then turning the Internet back on, I finally managed to get Chrome 137 working properly without crashing upon opening, or creating a new profile due to profile data corruption. ^_^

But that leads me to my next point...

PART THREE: Profile Mix-Ups & Missing Info

THIS is where I finally run into the problem described in the subject title of this post.

No thanks to the faulty Chrome update (discussed in Part Two) that first messed up everything to begin with, all of my account's information saved since then is stored in the User Data folder's 'Profile 1' subfolder instead of the 'Default' subfolder. Because of that, my 'Default' account was totally lost access to, & I was left to use 'Profile 1' for everything. Then, Chrome 138 came, & I learned to my dismay that ALL of my stored profiles were gone. I tried logging into my Chrome account, but it came with hardly anything--no bookmarks, no history, almost zero extensions & their corresponding data (never mind the ones running under Manifest 2!), or anything else besides passwords & maybe a few other things. Even with Chrome Sync on, nothing came up. Once again, the browser updates screwed everything up, & even worse than last time! Hence, I had yet another reason to revert to Chrome 137, restore all my original backed-up data, disable all automatic updates, & finally fix the damage that Chrome 138 had caused to all of my user data.

So, now that I've got my Default, Profile 1, & (unwanted) Profile 2 folders back in my restored User Data, all of my problems should be solved, right?

Wrong.

Unfortunately, some of the folders that came with earlier versions of Chrome (like Databases) don't show up in the new Profile folders in my Chrome Appdata--despite me downloading an earlier version to begin with!--so I must paste them back in from the hard/Flash drive.* In fact, for that matter, I need to reinsert any & all backed-up profile data files & folders that are inexplicably missing from the newer User Data.

To wit, here are pictures detailing what I'm trying to fix in my Chrome 137 profile folders...
https://i.ibb.co/wN2k40Q2/This-Is-My-Default-User-Folder-After-The-Faulty-Update-Full-Picture.png
https://i.ibb.co/60zhjnJn/This-Prof...ll-Of-My-Data-After-The-Faulty-Update-Ful.png
https://i.ibb.co/JFGrTn01/This-Is-T...Originally-Stored-In-Default-Full-Picture.png
https://i.ibb.co/FLHjb54k/These-Are-All-My-Extensions-Their-File-Folders.png
https://i.ibb.co/mV0hw3Mv/Not-All-Of-My-Profile-1-Extensions-Are-Showing-Up-Full-Picture.png
https://i.ibb.co/LDzzY7Mh/How-Do-I-Move-Everything-From-Profile-Folder-To-Profile-Folder.png

Here's the order in which I need to transfer all of the missing profile folders & files from Flash drive to hard drive:
First, the full backed-up 'Default' & 'Profile 1' folders must be resaved in the 'User Data' Appdata folder with all their complete contents. Next, the data put in the new unwanted 'Profile 2' folder needs to go into the backed-up 'Profile 1' folder, 'cause that's where it originally came from. After that, all of the backed-up 'Profile 1' data, needs to go into the Appdata 'Profile 1' folder. Finally, all of the information from the backed-up 'Default' folder, needs to go into the Appdata 'Default' folder.

But these are all of my questions:
1. How do I transfer everything from folder to folder without overwriting anything? And will I corrupt my profiles if I keep both the previously-stored data files/folders & the transferred ones?
2. Is there any way to merge data for browsing history, bookmarks, sessions, extensions, & all other stuff of that nature? And if so, how?
3. Will I corrupt my profiles by replacing the folders' original data for history/bookmarks/etc. with all of the merged data?
4. Should I keep Chrome closed while doing all of this?
5. How do I make 'Profile 1' my default account profile again? ** Or should I designate the original 'Default' folder as my default account profile, instead, like it used to be before everything got messed up? And if the latter is the case, should I ultimately move all of the data from my other profiles into "Default"?
6. How long will it take for everything to sync back up?
7. Can anyone help me, or would they like to, convert my Manifest 2 extensions to Manifest 3, so that I may use them on updated Chrome browsers away from my computer? ***

Any & all assistance would be greatly, GREATLY appreciated! ^_^ Thank you very much in advance! <3

---

* Hopefully, it'll work, since I have the last version of Chrome with the older API interface that will accept ALL of my original Chrome data folders, several of my previously-installed extensions that 138 is completely blocking, & all that...

** And after going through all this trouble of restoring my backed-up user data, even now that I'm signed in with sync on, I am facing the same issue that plagued me prior to rolling back: no bookmarks, no history, almost zero extensions & their data, or anything else besides passwords & maybe a few other things. Why is this the case, if my restored-from-backup 'Profile 1' folder has content in it? Is it because I earlier lost the whole 'Profile 1' profile, & I don't know how to get Chrome to recognize its reinstalled data? If so, what do I do about that?!

*** There are programs & ways to do that, but the best one involves using Python coding, & I utterly refuse to do that myself--it's too bloody difficult & time-consuming for me, & I've had nothing but trouble with it in prior experiences.

Never thought of using System Restore?

I'm not the best one to answer your question as I do not use Chrome nor will I ever, but I can give you my opinion on browsers in general..

You can not blame Google for the fact that old browser extensions no longer work nor that data for such extensions was removed when the browser updated. When browsers update (any browser) the developers of any extension MUST also update their extension accordingly to work with the updated browser. This is not singular to Chrome. Extensions have to be designed to work with the browser, not the other way around.

You do not say what browser extensions have been so important to you. The machine name in the list of your extensions list does not tell me what they are. The fact that your were running Chrome with what appears to be 49 extensions is questionable for me.

The only way I know of to go back to your state at a point in time when everything worked is to restore a full system image if you have one. Then the battle would be on to continue using an old version of Chrome. Even if you managed to stop Chrome from updating, that might prove problematic if you sync your Chrome data.

Otherwise, since your quest seems to have started 8 months ago with no resolution, you are beating a dead horse since Google is phasing out support for the outdated Manifest V2 extension platform. It is what it is.