Q: Can Present Perfect Continuous and Present Continuous have the same meaning?
Yes, there are often times when there is very little difference between the two, and they pretty much mean the same thing. However, your example is not a very good one.
Native speakers would not say:
He is taking the exam for the last 2 hours.
The problem with that sentence is the time reference back toward the past. We don’t use the present continuous is a context like that. Although we might say:
He is taking the exam for the next 2 hours.
to mean that he will be busy for the next two hours taking the exam.
However, we could say:
He is taking the exam in that room.
And also say:
He has been taking the exam in that room.
and those two sentences pretty much mean the same thing. However, the first one could be interpreted in a couple different ways. It could mean:
He is (currently) taking the exam in that room (right now).
but it could also mean:
When it’s time for him to take the exam, he’ll be taking the exam in that room.
The specific meaning would usually be apparent based on the context. For example, am I answering the question:
What is he doing at the moment? (He is taking the exam in that room.)
or did I answer the question:
Where will he take the exam? (He is taking the exam in that room.)
although in the latter case, I think many might be inclined to say one of these instead:
He will take the exam in that room.
He is to take the exam in that room.
The EF website has an interesting note about this:
USING THE PRESENT CONTINUOUS TO TALK ABOUT THE FUTURE
The present continuous is used to talk about arrangements for events at a time later than now. There is a suggestion that more than one person is aware of the event, and that some preparation has already happened.
I am leaving tomorrow. = I've already bought my train ticket.