How to do matrix conversions by row and columns toggles?

Question

I have got a square matrix consisting of elements either 1 or 0. An ith row toggle toggles all the ith row elements (1 becomes 0 and vice versa) and jth column toggle toggle

Answer 1

It's not always possible. If you start with a 2x2 matrix with an even number of 1s you can never arrive at a final matrix with an odd number of 1s.