Hello,
I would be happy to help. 
I can confirm that under that tag there is a single card currently tagged.
From there, I’m afraid there is a limit to how much accounting I’m able to give for v11, as v11 was a few years back (and pre-AnkiHub) thus a lot of the changes were quite some time ago. To the best of my knowledge there isn’t a 1:1 accounting for every single change (as at this point, there have been many tens of thousands of edits and updates in the last few years).
That being said, I’ll do my best to address your questions in order:
In short, if there are new cards to add they will be added. If there are existing cards that have since been updated, they will be updated. That’s about the long and short of it.
Notably, AnkiHub will not delete any cards (as it does not have the ability to do so) so no cards will be deleted.
Could be lots of reasons. It could be that the section in FA has changed over the last few years (resources do often change, sometimes yearly) and it has been a long while since v11 was active. It’s hard to say, ultimately, as v11 was pre-AnkiHub and long ago.
Without knowing which cards you’re referencing, it’s hard to say. The section that tag refers to is fairly elementary information (a few names of basic enzyme types), and so it may be that the cards were modified, deleted as being insufficient yield, or any number of other things. In short, I don’t have a record of v11 and so can’t speak to each individual card change, unfortunately.
At least some cards have certainly been deleted in the years since v11, that I can confirm as being the case.
Please let me know if that answers your question, and if there’s anything else I can help with.