Iphone 3gs from 4.2.1 to 6.1.6 and back

reefgeorge

I have an iphone 3gs that has worked extremely well with 4.2.1 but i would like to add whats app which needs 6.0+. i read many bad things about speed and latency problems when the 3gs goes to ios 5 or 6 so i would like to roll back everything if its a disaster. The ios has never been updated since i bought it new and the phone is not jailbroken. The more i read about shsh blobs, been jailbroken?, apple signed ios, ifaith vs... The more confused i get.

Can anyone tell me what i need to do in my specific situation?

Thanks,

George