Submit ipa to app store

Question

I looked on many question for submit ipa to app store. But nothing is very clear so here is my case:

A vendor has created application for us and he has his own certificate. Now as he is not able to send code to me but he can provide ipa signed with his certificate.

So I want to know if I resign ipa with my distribution certificate,will it work?

Also can I upload ipa through Application loader?

In some answers it was written that you need .app.zip so if in case ipa would not work,manually created .zip by compressing .app will work or not?

It is all confusing please guide me.

Answer 1

Yes , you can change certificate using this:Re-sign IPA (iPhone)

also you can use ipa file to upload it from application loader.