RUU Required after Wiping Internal Storage

Do I need to flash an RUU after wiping internal storage in TWRP recovery or can I flash any ROM that is compatible with my phone? I haven't accidentally wiped the internal storage, I am just curious.

Can i flash TWRP recovery without wiping phone??

So I have 2 Note 4's. One has issues, and is my wifes. So I am wondering if I can flash twrp on hers, back it up, then take the backup, and resstore it on the other note4? The reason I want to do this is she does not want to restore everything all over again. My only concern is if I flash twrp, does that wipe data and such??

How to restore my oneplus 3 after accidentally wiping it?

I was locking the bootloader of the phone. Unfortunately in hurry, i forgot that the phone gets wiped in the procedure. Now, is there any way to get the data back (had some really important files). Any help will be appreciated. Thanks in advamce.

Removed battery during wiping data. and now it is stuck on green android logo

I was resetting my HTC DESIRE 616 though recovery mode and during "Wiping data" it was taking too long...so i pulled out the battery and from then whenever I switch it on or try to boot into recovery mode OR connect it to PC or Charger it first shows HTC welcome screen and then stuck at a black screen With a Green Standing Android Logo with a Blue colored diamond rotating in its tummy.
What should I do now.
Please help.
The android logo screen looks like this image -