"Is he beside you?" and "Is he with you?" Is there any difference between them?
or exactly the same?

Question

"Is he beside you?"  and  "Is he with you?"   Is there any difference between them?
or exactly the same?

Answer

They pretty much mean the same thing, except beside you references that they are closer.  If you say someone is with you, they may be with you but not directly next to you.

Answer

Beside you=  is shoulder to shoulder (more or less)
With you = is he in the room - or accompanying you .

Someone can spiritually be with you too - or it can show allegiance