My OS is Windows 10.

I read online that I could take screenshots with the Xbox app. Then I went through the process of signing up for it (although I don't have an Xbox) and somewhere along the way I was asked to enter my Microsoft account -- I have accounts at Hotmail and One Drive.

Now what happened was that unbeknownst to me this put that Microsoft account "in charge" of my PC, so to speak, so that it became the main account in it, like an 'administrator' or something, and now every time I want to log in I have to enter my Microsoft account info.

Then to add insult to injury, now I just can't use some apps (like Advanced System Care) and any feature in Windows that requires me to click "YES" on that freaking box that comes up saying "Do you want to let this app make changes to your computer?" because the button "YES" is simply "grayed out", that is, dead. It's non-clickable. So because of that, I can't even use System Restore to go back to a previous point and see if that would solve the 'mandatory password' annoyance.

So my questions are:

1 - how do I change it to the way it was before so that I won't need a password to log in?

2 - how can I do to completely eliminate any link of that Microsoft account to my computer?

3 - how do I solve the problem of the not accessible apps and features?

I appreciate any help you can give me because quite frankly I'm starting to get desperate (and pissed off!) with this brand new Microsoft screw-up.

Thanks in advance.