Has Been Solved or Resolved?

Resolve is used to mean the end of a conflict--"The differences between the two parties were resolved." Solve is used to mean the solution to a logical problem--"He solved the math puzzle."

Has been resolved or have been resolved?

Both are interchangeable but "it is resolved" is more frequently used. Besides, "before it is resolved" is correct while "before it has been resolved" is unacceptable.

Is solved and has been solved?

The difference is in whether you want to emphasize the state of being solved or the action of solving. "is solved" indicates that it is in the solved state. "has been solved" indicates that the solving of the problem has been completed, which is really just what it means to be in the state of being "solved".