[Q] HELP ROOTING ON BRAND NEW GS5 never rooted before topic

My problem is I have searched EVERYWHERE to find info on how to root my device being that it is brand new never rooted running the newest firmware update. My gs5 came with NI2 and then when I turned it on it did more updates so now it has NK2 NEVER ROOTED BEFORE. so I need to find out if I can downgrade my firmware back to NI2 so that I can use towelroot to root my gs5 because im feeling kinda sketchy about downgrading after the bootloader has been updated to NK2. and my next question is, ive read that in order to get on the most recent firmware and rooted you need to flash the firmware in order using odin till I get to the newest firmware and my question is this, after ive rooted and I flash new firmware using odin will my root still be there even after doing this 2 or 3 times getting to the newest firmware out will my device still have root? or will all the flashing of new firmwares take away root? so I believe if somebody answers these questions i'll know where to start.