How to Dynamic ID (do some bosses in icc in heroic and others on normal)

Hello, I have a few questions regarding the Dynamic ID feature:
- For ICC 10 does the kingslayer have to have killed Lich king in 10m or is 25m sufficient?
- If the kingslayer is saved to the instance can he change to heroic on a different raid ID which is already 2 bosses down?
- If its 10 man does the kingslayer have to enter the raid to change? If so does someone have to leave the instance to make room for the kingslayer? Can the one that left to make room enter again once the kingslayer has left?

Thanks in advance.

hello,

1- no
2- no
3- yes, yes he leaves or just dc inside, yes

Thank you for the answers.
I have one more question: Does the kingslayer get saved to an ID when he changes to heroic on an instance with some bosses already down?

No if he does not accept the ID and leaves within 1 minute