How do I know If my phones Bootloader is locked or not? I want to flash TWRP &amp; SuperSU to take a backup, but I read that if you flash TWRP with a locked bootloader it would brick my device &amp; wipe my data, now that would just defeat the purpose. How do I determine if my device bootloader is locked or not?

I have enabled developer options, enabled USB Debugging, there is a option in the menu 'OEM Unlock', what does it do? Does it wipe data?

Device - Samsung Galaxy-J700F
to just answer your question, and without needing any software, you can start your phone (or tablet) in bootloader mode by holding the  volume key and the power key from an OFF state. the software will then tell you the info you want.