Android phones, apps and tablets

very very easy. Do you know what recovery software they have put on it ?

Probably ClockworkMod (CWM)

1. Optional, Titanium backup Apps+User Data
   
2. Basically, find a rom for your phone on XDA Developers.
   
3. Download it, put it on the SD card (via USB xfer, whatever).
   
4. Reboot into CWM
   
5. Hit Factory Reset
   
6. Select Flash ZIP
   
7. Find the Zip file with the rom
   
8. After flash, wipe all Cache's
   
9. Reboot
   
   

Enjoy