mrrrrreow meow :3

What if I go into politics and start mrrreow meow :3 in EU parliament?

If you rooted your phone you can use Neo Backup can’t backup full ROM, but is great for backing up applications configured. For non root, I honestly don’t know. There are other applications for backup but I used this one and is easy to use.

I think you need custom recover or however is it called. TWRP is popular one, where to get it, idk try looking at xda forum for your device. I think you need to flash TWRP (or any other custom recovery) using Odin, and then boot to custom recovery and from there, using sd card or I think you can use adb sideload flash the rom you got. (memory wipe is needed before flashing rom). Where to get the recovery file depends on your phone model.