I finnish my beer its fully carbonated and bottled on 22 oz bottles (co2 comes from priming sugar)
now.. can start the pasteurization process ? or that only will work with forced carbonation beer ?
Pasteurizing home brewed beer is rarely done for two reasons: it's complicated, and you don't really need it.
Pasteurizing beer is done in industrial breweries to preserve the beer and kill all residual yeast, because the brewery wants the beer to remain 100% the same once it goes out the door. This is not as critical with home brewed beer. Furthermore, the yeast in a homebrew bottle acts as a natural preservative by removing the oxygen from the beer (and about 30-40% from the head space as well) which gives the beer an extended shelf life.
Bottom line: if you practice good sanitation and bottle condition your beer you don't need pasteurizing!! In fact, pasteurizing a bottle conditioned beer kills the yeast and prevents it from further developing the flavor of the beer as it matures. So for a bottle conditioned beer pasteurization is in fact the last thing you want!
Also note that pasteurization destroys some of the flavor. This is fine for industrial lagers that have little flavor to begin with, but not for a home brew!
To answer your final question, pasteurizing can only be done on the fully carbonated, packaged beer. The beer is force-carbonated, bottled, capped and then pasteurized, bottle and all.