Does an alpha order physically stop the নেকড়ে-মানুষ from breaking it. Like it Jacob literally unable to say he is a werewolf অথবা is he just not allowed to???

Yes, the Alpha order makes a werewolf physically unable to defy the order. The only exceptions would be if the order went against an imprint in some way, for example if the order would harm that imprint অথবা if they were ordered to lie to the imprintee, and of course if the werewolf being ordered could fight against the order দ্বারা claiming Alpha status himself (but that's basically only Jacob).