Sounds right!

Eric, what John A is saying in 3 pictures ..

Scenario #1 - No rule broken. 
Yellow is not caused to alter course during Red's tack and is not forced above close-hauled course after Red passes HTW. Red initially gave Yellow room to keep clear when Red fell to a close-hauled course and gained ROW, therefore Red did not break RRS 15.

Scenario #2 - Yellow breaks RRS 11. 
Cyan completes her tack without Yellow altering course and Cyan initially gives Yellow room to keep clear (no RRS 15 breach).  Yellow does not owe Cyan mark-room, but she must keep clear of Cyan under RRS 11.  Yellow, forcing Cyan to leeward, did not keeping-clear of Cyan, and broke RRS 11.

Scenario #3 - Purple breaks both RRS 18.3 and RRS 13. 
Yellow must alter course while Purple was required to keep clear under RRS 13, therefore Purple breaks 13. The incident occurs before Purple obtains ROW, therefore RRS 15 did not apply at that time. Yellow is also forced to sail above close-hauled after Purple passes HTW from port to starboard inside the zone, thus Purple also breaks RRS 18.3.

Ang - I was looking at the scenario pictures and I think there is more detail needed in Scenario #2. Are you assuming that Yellow is not close-hauled or comes down on Cyan forcing her to miss the mark? Because if Yellow is close-hauled and would have to go above close-hauled to keep clear of Cyan trying to shoot the mark, then, Cyan broke 18.3 since she caused Yellow to go above close-hauled and isn't entitled to mark-room because 18.2 doesn't apply.

On a separate topic about 18.3 - when does 18.3 obligations of the boat tacking from port to starboard end?
1. After the mark has been rounded/passed by the starboard fetching boat?
2. While the boats remain in the zone?
Argument for #2 is Team Racing call E-15.

I've reviewed the rules in light of this new understanding and come up with-yes #2 is the correct answer since:
1. 18 continues to apply until both boats are out of the zone by 18.1(a) first sentence and no exceptions apply.
2. 18.3(a) applies and thus not only does 18.2 not apply, but also 18.1(b) doesn't apply since no mark-room is owed to the inside boat that was the port to starboard tacker.
3. There is nothing that turns off 18.3(a) until one of the boats tacks which of course means 18.1(a)(1) turns off 18 or both boats leave the zone.

Ang thanks I see your scenario does mention Yellow forcing Cyan down below the mark. Agree 11 is broken in that scenario. Thanks for digging up the 2018 reference to 18.3 not ending until the two boats leave the zone. That was an interesting learning.