A: You can Memo the v4 at any point during the sequence. As noted in another answer, you can save the other player the trouble of deciding what to discard, or you can wait until they’ve discarded their card and even announced what they are changing. That’s all one big game action and as long as you announce your Memo before the next game action, you are fine. However, no matter when you Memo the v4 Time Car, they do not lose the discarded card, just the v4 itself.