How to prevent a user from accessing a local drive?

Question

System administration

I need to prevent all users (without admin rights) from opening and browsing "Disk D".
OS: Windows 7
1) Decided to do it on the test folder: banned the "Users" group from all actions (opening, viewing, etc.) for the test folder, but even I myself (administrator) cannot open this folder. My administrator account is not a member of the Users group, it is only a member of the Administrators and HomeUsers groups. I denied access to the test folder only to the "Users" group.
Why can't the admin account access the test folder then?
2) I'm considering the option to generally remove the "Users" group from the list of those
(in the screenshot this is the "Groups and users" section)
If I do this, can I later add the "Users" group to the list of those who can view the "D drive" again?

PS Please answer point by point (numbers). I specifically used them and made the questions as specific as possible so that it would be convenient to perceive the information and not lose important details.