Grammar

1)If I give a deposit to a receptionist at a hotel and I want to make a joke and ask if I'll get back less money, could I say something like: Does it come with interest?

2)The contract cannot be in breach of law. (It has to be in accordance with it.) Is this correct?

3) If I want to claim my right to an estate and I have to sue someone, how do I say that I have to 'enforce my right through lawsuit'. This version sounds rather clumsy. I want it to be slightly formal though.

Thank you.