Yellow, a leeward boat, luffs head to wind, and Blue luffs in response, so that both reach positions side by side, head to wind. Blue continues to change course and passes head to wind. In so doing she makes contact with Yellow. There is a Y-flag. What should the call be?

If, when Yellow begins her luff, Blue immediately responds and continues to do what she is able to do to keep clear throughout the incident but there is contact anyway, then Yellow is not giving Blue room to keep clear and she breaks rule 16.1. Penalize Yellow.

If Blue could have kept clear, but either responded too slowly, not enough, or over rotated, then Blue has broken rule 11 or 13.1. Penalize Blue.
Question 2
In similar circumstances, Blue responds and when head to wind, she remains so for a time. Then Yellow bears away and their sterns make contact. There is a Y flag. What should the call be?

Answer 2
If Yellow's change of course immediately results in contact with Blue, Blue was not keeping clear and broke rule 11. Penalize Blue.
If there was more distance between them, and Yellow bears away hard giving Blue no room to keep clear, then Yellow breaks rule 16.1. Penalize Yellow.
The umpires' decision is based on the distance between the boats, the nature of Yellow's bear-away and the efforts of Blue to keep clear.
Question 3
In similar circumstances, Blue keeps clear, but when head to wind, she maintains it for a time. Blue then passes head to wind, and slightly later Yellow bears away and their sterns make contact. There is a Y-flag. What should the call be?

Answer 3
When Blue passes head to wind, the boats are no longer overlapped on the same tack and the second part of the definition of Keep Clear no longer applies. If the contact would have occurred without Yellow bearing away, Blue broke rule 13.1. Penalize Blue. If the contact would not have occurred without Yellow's bearing away, Yellow broke rule 16.1. Penalize Yellow.