1. The idea of the "death canonpoint" is that they are in Tokyo-F to be revived, so if they, for example, canonically died on Monday and was revived on Tuesday, you can have them be from Wednesday, but some sort of non-canon incident would have killed them again.

2. They don't need to be dead in canon, no!

3. Normally unappable characters will not be allowed to app into imeeji even after the 4th wall, unfortunately.