A: Short-term supply, even if it is in the school where you have a part-time contract - either with the school, a supply agency or local education authority - does not count towards induction. The work would count only if you had a term's contract. You could have part-time work in several schools - say, one day in each of five schools. All that work would count towards induction as long as one school took responsibility for you.
If the teaching you do as part of your contract is partly or entirely made up of a subject other than your specialism, then you will still be judged against the induction standards. That seems tough, but people should give you help with the subject knowledge that you need.
See the Teacher Training Agency's website (www.tta.gov.ukinductioncalculator) for an online calculator that helps you to keep track of how much induction you have done and how much you still have to do.