Question Got a buncha questions for you guys

Hello, my roommate has a Verizon Galaxy S3. He recently took the 4.4 update, and it apparently screwed up his phone pretty bad. He gets terrible battery life and force closes and freezing. He came into my room knowing that I'm an android nerd and he asked me to root and rom his phone. Cool.

So, now I'm trying to catch up on the current state of the GS3.

He has never rooted or installed recovery. I was under the impression that the Verizon GS3 had an unlocked bootloader, but now I'm reading that the bootloader might be locked since he updated?

1: Is it possible to ODIN back to an earlier version and then unlock his bootloader?

2: What's JTAG?

3: Is there an easy way to install recovery on 4.4 that I'm missing?


Any links or advice you guys could give me would be really helpful... I'm currently reading and jumping between links, but It's hard to figure out where the phone currently stands with all the conflicting information out there and the new update that just pushed.