I honestly don't know. Anything I told you about that would purely be a guess. Just don't know much about AMD (and particularly Bulldozer) OC'ing.
can i get 4.5ghz at 60C with hyper 212 ?
Maybe, if your ambient is below 20c or if your chip takes minimal voltage to reach 4.5ghz
AFAIK, To run a fx8120 @ 4.5ghz, you'll need a top tier cooler like the NH D14 or the H80.
4.2 is reachable with 212 evo i believe if i can get 3.8ghz with a stock cooler at 50C
3.8ghz @ 50c with stock cooler is great. your ambient must be quite low. Yes, 4.2ghz might be a fair OC. what happens is, for 4.5ghz your voltage will most probably exceed 1.4v, hence the 212 evo might have a hard time.
4.64 is the highest semi-stable OC i could get with my hyper 212 evo.
4.0 and super stable with evo even under heavy load.