Im not very professional in cheating but some questions i can answer.
About bypass i dont know nothing. I think they code it in C++ or something.
How to find addresses? I dont think its hard. If you have brain on good place its no very hard. You have to think... like for weapon: Choose weapon like colt (its number 2, you can find weapon values on google or something) and you start to scan for value 2. Next: choose like m24 and press next scan NOW FOR value 29.
If you want to find more complicated addresses like stamina or something you have to start scan for unknown initial value then just - think - go and decrease some stamina then scan for decreases value, wait for stamina increase and scan for increases value.. do it that much as you have good address.
How to make UCE? (Undetected Cheat Engine) I dont prefer to download it from internet. Better is make it yourself and be 100% sure that its undetected. You have tutorials in tutorial category on MPGH. (Mentals tut is very nice one)