Default [Q] Planning to buy a second hand lg g2 32 gb

Hi, I'm planning to buy a second hand lg g2 32 gb d802 international edition. I have the following questions:

1) Is it possible to root LG G2 32 GB D802 International edition (currently running android 4.4.2 stock official) and then regain warranty completely i.e. removing "ROOTED" from download mode and getting "UNROOTED" in download mode?

2) Any tips which you would like to give me before accepting the second hand phone? As in, checking download mode, checking status says unrooted in system settings etc.