General Architecture Question

Hello! I’ve been developing php web apps for 10+ years, and am working on my first Ionic app. I have just a few very basic (possibly stupid questions). The app is really just a simplified version of our main app which is designed for tablets and desktops. My main reason for using Ionic/Cordova is to get the app into the app stores.

-Is there anything wrong with just switching out ionic tags for html tags and using all my same php functions (albeit simplified) for server side processing. My app essentially becomes a super simple website spit out in Ionic tags.

-If above is true, can I rely on the app essentially behaving like it’s running inside a browser on users cell phones? That is, I can use cookies to store persistent logins and session data just like in my main app.

-How are push notifications best handled?

-Is there a chat/messaging app like Comet Chat that plays well with Ionic/Cordova??

Thanks in advance for the push in the right direction.