Can a player play two Reinforcements to reinforce two units at the same time or two Jundland Terrors to attack with Bantha twice during Start of Round/End of Round?

If yes/no, can you link to the source of the ruling?

Thanks in advance.

You cannot perform the same ability twice in the same timing instance. (core rules) This includes identical command cards during start of round or end of round. Also ruling in the FAQ thread here.

· A player cannot play multiple copies of the same Command card at the same time.

Also, if a massive figure ends movement on top of figures, it cannot move again during the same activation, start of round, or end of round. Also ruling somewhere here (use google), or wait for the next FAQ.

So I suppose that would also prevent multiple Jundland Terrors from being played even if you had two Banthas?

Yes. Just like you can't play two Reinforcements even when you have two Trooper groups with defeated figures.