Stardust Dragon ruling question.

If i have macro cosmos activated on the field and negate mirror force with stardust dragon; will he come back from banished?

No

"During the End Phase, if this card negated an effect this way during this turn: You can Special Summon this card from your Graveyard."

"Stardust Dragon" has to be in the Graveyard during the EP in order for its summoning effect to activate.
Since "Stardust Dragon" is not in the Graveyard during the EP of the turn, it cannot be brought back from it.

The answer is indeed No.

Card effects do not "assume" that you're Special Summoning them from somewhere, they usually specify from where they Special Summon themselves.

Question Answered

Black Cat