User blog comment:B214/General Discussion/@comment-27180505-20170331135923/@comment-82.60.161.59-20170331221547

Vritra promotion is not Saji transforming into Vritra, even because he cannot do it, he doesn't have all Vritra's sacred gears. Anyway, with Vritra Promotion Saji doesn't really become the dragon king itself, he is envelopped by his black flames which assumes Vritra form.

Regarding Issei, no. Issei's body parts can dragonify only if he sacrifice them to Ddraig and they will stay so unless Akeno and Rias suck the dragon energy out of him through his fingers. This is the situation until what happens to him after he fight Shalba for the second time.