A. First of all, congrats on getting multiple requests for the full ms.
Now, on to your question. The best etiquette is to simply be honest. Reply to Agent #2 (by e-mail, hopefully), saying how excited you are about their request for the full text, but you regretfully have to inform them that it is in the middle of an exclusive read. Ask them if you can send it to them in a few weeks when the exclusive period ends, providing Agent #1 has ultimately said no to the project. The quicker you can do this and reply, the more professional it seems.
If Agent #1 says no and Agent #2 hasn’t answered your question, I advise sending it anyway. They wanted to see it, and they may have not replied because they were momentarily frustrated that you couldn’t immediately send it. But, still, they did want to see it, so send the requested ms over to Agent #2 ASAP.