1. Explain the reasons of Romeo and Juliet's suicide. Did they have another choice?

Really good question the answer is yes. They could have kept away from each other to keep from that happening

It wasn't fate. It was pure stupidity - they acted foolishly before thinking through their actions. If they had thought through their actions before rushing in they might have not died at all. The entire thing could've been avoided totally if Romeo had handled Tybalt better, and had taken responsibility for his actions instead of running away.

But that still didn't cause their death. What caused their death was Romeo assuming that Juliet was dead - instead of waiting for the letter that would've explained the situation - and killing himself. Juliet killed herself in a rush of illogical emotion. They died because they were irresponsible children who acted before they thought.

And because Shakespeare wanted the play to follow the earlier Greek play and be a tragedy.