Solved Upgrade from Win10 Pro to Win11 questions

Am thinking about upgrading to Win11- have 2 questions:
1- must I change file system on all 3 of my drives or just on my boot drive from MBR to GPT status?
2- I installing Win11 & finding I do not like it- can I change my GPT drive(s) back to MBR without any problem?
Thanks in advance for your response.

You opened a thread on Tenforums with same subject

@ljdarby
Please edit your profile with ALL your hardware specs. It will help us to help you
System Specs - Fill in at Ten Forums

If your computer meets the hardware requirements, you can convert your Win 10 drive from Legacy-MBR to UEFI-GPT and then upgrade to Win 11.
Convert Windows 10 from Legacy BIOS to UEFI without Data Loss

As things can go wrong, we recommend that you create a drive image backup from the current Win 10 drive and save it on another drive.

Same answers here that you got on Tenforums (why were you expecting different answers?)
1. On the drive the computer boots from needs to be converted to GPT and UEFI booting.
2. You do not need to return the drive to MBR in order to restore Windows 10. You just need to switch to booting Windows 10 in UEFI mode. But, if you really want to go back to MBR, you will need to make a system image backup of the MBR drive before you convert it to GPT. If you want to go back, then restore the system image backup you created.