If someone blocks you on YA, does that mean you can't answer their questions anymore?

Yes that is what happens when you are Blocked.
When You are blocked you cannot answer questions they ask but will see the question.
You will not be able to comment on answers they give on questions either but you can comment on answers given by other users on their questions.

You will not be able to email them using the Y!A email and will not be able to see all their Q&A on your profile even if not private.
You will not be able to Follow them if they allow Followers.
You will still be able to report any questions they ask or answers they give and if level 7 you will still be able to move their questions to different categories.

yes or see there questions

That's exactly what it means.

Yes , you will only be able to see the question.....

Correct.

I'm pretty sure that it means that you cannot even see their questions, therefore you cannot answer them or use the thumbs facility etc.