Will you still be here? or Are you still going to be here?
Another way to say it in Indonesian is "Apakah kamu akan TUNGGU di sini" since there is no prescribed timelines.
"Will you be still here" should be accepted too! Come on!
Not really. You could say it I guess but it would be extremely informal.
Is "tetap" in this context a verb?
It's a modal marker like "akan" before it. I think grammarians consider modal markers to be verbs but I could be wrong. The main verb is "berada"
Tetap = still
When does "tetap" mean "stay"?