Can I manage two Apple accounts?

The iPhone is intended to be a single user device. There is no user interface to add users like there would be on a Mac. Attempts at signing out of one account and signing in with another is going to merge data across both accounts and be a problem.

If you are attempting to do something else, please describe what that is.

Two accounts on one device would be very difficult. Exactly what is it that you hope to accomplish? Why do you want to do this?