I'm working on a new project for the next month or so, but, I'm not using my computer ... my concern is how to keep this computer configurations untouchable, or how to restore them. I may add a restore point and restore afterwards, or maybe add a new user account, but I like neither of those, so does anyone know some short of sandboxing that I can use to install some apps?
Do the work in a Virtual Machine.
You can look at differencing disks to allow undoing changes in the VM, and at the end just delete the VM if you don't want to keep it.
Remember the VM (guest) will need patching and anti-malware as does the host.