Is it true that in every professional tournament of Dota 2 , two teams cannot choose the same hero? And all your teammates also cannot choose the same hero?. In other words we MUST use 10 distinct heroes in total for each game ? For example if I use Invoker then all other players including my teammates are not allowed to play Invoker?
That's correct. In most Dota 2 game modes, duplicate hero selections are not allowed. This includes Captain's Mode, which is the the primary mode used in tournaments.
The exception is Mid Only mode, which can only be played in private lobbies. In Mid Only mode,
Creeps only spawn in the middle lane. Duplicate heroes allowed.