I am most disturbed by the fact that Panera was granted some sort of "sandwich" monopoly over an area than any ambiguity over terms, which exist practically everywhere. That said...
Cake is not bread (though that distinction can be fuzzy, ie banana bread), so that would rule out pop-tarts and ice cream "sandwiches".
My intuition leans towards Adriennes "sandwiching" requirement, which could include wraps because of a "sandwiching" action. Hard tacos may be excluded because of lack of "bread" and the "sandwiching" is usually unsatisfactory. Soft tacos may still be ok. If you don't like hot dogs being referred to "sandwiches" don't "sandwich" them. Corn dogs would not be "sandwiches" for example. Half "sandwiches" are fine as long as there is "sandwiching" applied.
Open faced "sandwiches" are like one hand clapping.

Btw, the naive acceptance of the facts as given reminds me of a description of a peculiar situation:
At the ski resort:
young women were looking for husbands and
husbands were looking for young women

Assuming it were symmetrical would get you in trouble.

Someone cleverer than me could probably put this in the same form as these questions.

(ht K T Cat)

I don't see how both 10 and 15 can both be as evaluated.

In q10, I can see where the supporters are going with this and there is a formalism that I am not familiar with (though I think that makes it more of a shibboleth than a neutral evaluation). I wondered in general how we are supposed to know what hasn't been assumed by the questioner. I fell into that trap. If you don't think the questioner was assuming stuff, go to q15.

For q15, though, many supporters seem to be grasping at stuff that wasn't mentioned either. (deuterium, water-like substance) We are given a straight fact, then essentially asked whether that can change. The same sort of lack of "play" that is in the word "Paris" should apply to "water" was well.

Phil, you said it well, also.