Can you be asked to be induced before your 40 weeks? I can hardly stand without my ankles hurting because I am so heavy. Just wondering.

Not safe. Unless medically needed, being induced is not a wise thing to do for your ankle situation. Your baby's health is much more important for now.
39 weeks. You should not want to be induced prior to 39 weeks, as complications rise with inductions prior to that gestational age. Keeping your feet elevated will help with swelling.