A grammar for my context free language {xy | x, y ∈ {a, b} ∗ , |x| =|y| , x != y}
There can be multiple grammars for one language, all equally valid.

We generally don't check solutions to exercises here.  The way to tell for yourself whether your answer is correct is to prove it correct: see How to show that L = L(G)? for techniques on how to do that.