Third Hand Play - should you return your partner's suit or switch to a new suit?

Here are the hands played during the video:
1. You win the first trick. As you have control of the diamond suit, the right play is to continue spades. You plan to knock out the only entry to dummy, and then hold up your ace of diamonds tinyurl.com/y5... POLL 1 Play at trick 2
2. That suit in dummy is likely to run, (declarer or partner has QD) so switch to dummy’s weakness tinyurl.com/ny8... POLL 2 Play at trick 2? (Down 1). There is a clue from the bidding to attack clubs rather than hearts.
3. With that long suit in dummy, switch to a heart to knock out dummy’s entries tinyurl.com/k8j... POLL 3 Play at trick 2?
4. East starts by signalling encouragement, but then must overtake in order to lead into dummy’s weakness tinyurl.com/ycj...
5. Hand 3: Only 50% defeated 3NT: tinyurl.com/y9d... POLL 4 Play at trick 2?
6. You must overtake KD at trick one to lead a club. No one found this defence: tinyurl.com/2e... POLL 5 what to play at trick 1?