Is this sentence OK?
(I mean that's besides the point)

If I say;

That's a subject of different discussion.

Question

Is this sentence OK?
(I mean that's besides the point)

If I say;

That's a subject of different discussion.

Answer

I'd say "that's a subject for a different discussion" or "that's a topic for a different discussion".

But usually when someone says something is besides the point, they mean that it is irrelevant and does not pertain to the current discussion. It does not usually mean that they want to discuss it later.

Answer

Better to say:  that's another matter.

Answer

Yes, although you would say, "That's the subject of a different discussion".