LG G3 Cat.6 — LG G3D855 & LG G3D850; Whats the difference?

I keep seeing people talk about the G3's and the Lollipop update and Rooting the phone but its always referring to the D855.. I have the G3 D850 that I got about 6-8 months ago and it came with 4.4.2. I got a small OTA update couple weeks ago that changed my end build letter from "d" to "f" and google maps got a Lil facelift, but other than that not much has changed... My ???? Is.. What's the differences in the models and I have had trouble with my File Manager,(always wanting to make duplicate or empty files).. I'm learning about Android OS in a "crash course", so if anyone can give me info or tips to help me learn more about this phone, I would greatly appreciate it Cuz I'm at the stage that sometimes when I try to clean up files or apps I occasionally do so with my fingers crossed hoping I dont wipe out the important stuff.. Oh yeah my phone is UNrooted!!
It did mess up on me one time where the apps on screen were not stable, found out an app at stole my RAM, so had tech clean it up, G3 is fast and love the flow of it but t when RAM gets full it acts like flip phone from 1997!!! ). But yeah any pointers would be awesome....