Question about making changes to a project

I have some questions about changing a project. (1) Lets say I currently have Project A with 50 devices. Now I create Project B with the same 50 devices but totally different design. I know I will have to activate all the devices again for Project B, but will I have to reset the devices first before adding them to B? (2) Now, let's say I want to go back to Project A, can I load that to the repeater and will the repeater find the devices or will I have to activate the original devices all over again? I'm wondering if the project file includes some kind of MAC address or serial number for each device so that I don't have to manually add them. (3) Final question, let's say that instead of creating a new project I just update the project, save it on my computer as Project A-B then load to the repeater. Would it be possible to load the original Project A into software, load that into the main repeater and revert back to where I originally started? Thanks in advance.

Not sure if it makes a difference but for question 3 above, but I don't mean B will be completely different. Just rename some rooms/locations/zones and add a few devices. "Project A" was designed by someone else, but it's not quite right. I need to fix it but being new to RR2 design, if I screw things up I want to be able to revert back to the original design without any pain. So how do I create a restore point? I suppose a 4th option would be to save Project A as a file called Project A Backup before making any changes and then make my changes to original Project A. If I screw it up, can I just delete the screwed up Project A file, rename the project file Project A Bakcup -> Project A and load that to the repeater? Will I be right back where i started?

Once a device is activated it will not be recongized by another system until you reset it back to factory defaults. This is what prevents your neighbor from enrolling your devices in their system.

If you save your original program A as A1, you can always go back and load A without reactivating. You will loose your changes in A1 but everything else will work.

Thank you!