Ask yourself this - If you were about to invest in an App, would you ask the dev those questions? They seem fair imo. Imagine if you were pitching to Y Combinator - would any of the potential investors ask those same questions?

Equally it could just be someone on a fishing expedition to see if it was worthwhile developing a competing app so do some background research of the potential partner to see if they are either a VC or a possible copy-cat