Re: Possible? Yes. Probable? No.
It is possible, theoretically, to make a secure app
Not in that formulation it isn't. "Secure" doesn't mean anything, in a technical sense, except under a threat model, and you haven't specified one. And for any non-trivial system under any non-trivial threat model, "secure" is a probabilistic claim, not an absolute one.
So in fact it is not possible, theoretically or in practice, to make a "secure app".