Two questions:
1) Could I roll for Trelane's IMG&MR 1rst AND THEN roll for IRUSG after and then use the set aside D6 roll to replace Suited Henchmen's roll?
2) is there any difference between "Starts the game" and "At the beginning of game"?

EDIT: I belive this nullifies my question:
Lets say same question with smww060 Mr. Mxyzptlk

They "start" the game before they're placed in their starting area, before Mxy's d6 is placed on his card.

OK gotcha, thank you!

Though if a Suited Henchman were brought in by the Gotham Crime Boss trait, you could replace that d6 roll

Yeah I did see that. Thanks again

To address this specifically, yes, there is a pretty significant difference. "At the beginning of the game" is a triggered effect. It can only ever happen at one point, Step 5 of the Beginning of the Game Sequence. "Stars/Begins the game", however, indicates a passive effect that applies whenever the character is brought into the game for any reason, ie; from the Sideline via effects such as replacement or ID Cards, of effects that bring characters in from outside the game. This is why things such as Green Arrow start with his Arrow tokens when Called In with an ID, or Doctor Fate gets his Helmet, etc. If those were "at the beginning of the game" triggers, they would not get those effects.