Hi, I'll submit the application to petition for my brother and his family's immigration to US. I wonder if he can still get visa and allowed to enter in US as a student or a businessman depending on opportunities while he is waiting for the immigration result.

thanks for your help!

Your brother can probably enter the U.S. on a different visa while waiting, but the problem is that the purpose of the visa must fit regulations for getting it. You cannot land in the U.S. on a tourist visa and say to immigration that you are just waiting for your immigrant visa to arrive in the mail. For that you will be deported and also spoil the current immigrant visa that is in process. So, I would have been very careful doing this. If you want to be on the safe side, then wait.