Q: Is Apple fixed layout epub supporting two languages in one ebook

As long as you don't try to make your main language one of those which the iBookstore does not yet support, I think there is no limit to the number of languages you can include in a book, regardless of format.

http://m10lmac.blogspot.com/2014/02/languages-not-yet-supported-in.html

If you are talking about having different language versions of the same text which the reader can select via some sort of button, I do not think that is possible.