"See you, Vanya!"
Only if "see you" and "good bye" are the same! Is it? "See you" - "увидимся". "Пока" - "bye". Or whatever...
They're both fairly informal ways of parting. Either should work as a translation here.
if Пока is going to be another translation, then thwy really should put that as one of the translations.
No, it's an informal form of "Иван" used between friends and relatives or when addressing a kid.
William - Bill ( Billy ) Richard - Dick ( Rick ) Robert - Bob ( Bobby ) James - Jim ( Jimmy ) Jonathan - Jack ( Johnny )
Not the exact same thing, but same idea (I'm not Russian, someone correct me if I'm wrong)
My question is.. Does every Russian name have an informal form?
Yes, all Russian names have an informal form. Анна = Аня, Анастасия = Ася would be ONE of the informal forms, etc. etc.
Only as Ваня, not Ваниа. Why not - that seems a strange question to me. Like asking why we write Robert instead of Robbert in English.