thank you for showing us your anwers.

The working in the question is not completely clear.

It is hard to make the wording exact for questions like this.

But yes a and b are correct.

c) there are 6 different 2 coloured squares. But lots of each.

So he has 6 to choose from for his first and 6 to choose from for his second = 36 if he can choose 2 the same.

If they both have to be different then he has 6*5 = 30 possible choices