Am I understanding correctly that sburb (under normal circumstances) is basically sacrifices one planet to create a universe? If so, does it mean civilization advanced enough to have colonies on different planets can have frog temples on multiple planets to increase the chance of discovering the code of the game?

I mean in a way. It’s hard to say though because Alternia had exactly that, but also something that made every Troll in the Universe die, so maybe the price to pay is the entire civilization falling in some way? Whichever the case, it’s possible the same Universe could have more than one Frog Temple, and it’s also stated that, if the Exiles rebuild the civilization in the dead planet, it may be viable for yet another civilization to give SBURB a try again.