I think you're very very confused.
1. I didn't see it said, have you looked for BT offers on discovers site?
2. Are you aware bt apr and purchase apr are two separate things? It matters 0 if your in an interest period on a card, balance transfers generally have their own apr(some the same as purchase apr).
3. You can bt from chase to discover to chase to capital one to chase to capital one to discover to chase to capital one and back to chase. Good luck with the fee's.