Hardware 3DS System Format

[AchakClaw]

Soon, after my 3DS gets repaired (it's about to completely break externally), I am planning to format my 3DS for a fresh start.
Currently, it is HACKED so I plan to back up the entire SD card, un-hack, format, then hack again and restore everything. I do have a few questions..

• Can I restore the entire SD card when I un-hack, format, and hack again?
• What can be backed up and restored from the SD card
• I understand my friend code will be changed, so what will not work with a different friend code?
• Can I back up everything for all software (including Swapdoodle) and restore it after I re-hack everything again?
• Will I have any problems re-hacking after I un-hack it? My friend did something similar, except he formatted before unhacking, and his DS is causing issues..

Important notes would be nice to, before I wipe everything. Advice is good too
Sorry if I sound like I'm asking a lot