Me and a couple of friends are planning to go visite a friend who is graduating but one of my friend is a dreamer(daca student). Would he have any problems entering a military base on the day of graduation?

If he has some sort of government issued identification he should be fine. For example his work permit, a drivers permit, or drivers license.

No shouldn't have any issues. If he can't get in he wouldn't have issues anyway, but just go in amd present your Military ID.

No

Only issue would be if your friend is not here legally.