Can i use 2 of Matrix_And(n) it the implementation?

I don’t see why you would need to, but you may use it.

In order to check self loops and undirected graphs, the tool we created in former exercises returns a new circle, instead of returning 1/0 for applying for the requested statement or not. Therefore the best option I see would be to use matrix_and_8x8 to compare if they are identical. The circle I did in exercise 13 passes the tests of the “bodek” email but I didn’t receive a 100% of passing, and I can’t find the issue with any of the inputs.

What would you suggest to do to reassure it?

I see the direction you’re going in, but I will pose a counter question to you: Is it necessary to compare the entire matrix before and after removing self loops, or is there a simpler (also computationally cheaper and faster) way of checking for the existence of self loops based on particular elements in the matrix?

Regarding finding issues in your implementation, there are only two approaches you can take. Either try a lot of input combinations and check if the output of your circuit is as expected, or try to analyse your design from a theoretical point of view and identify your mistake.