Android Question should i use B4X pages for a Push Notification app?

The real question is whether you want to support multiple orientations or not. If not then use B4XPages. It will not make anything more complicated and it will make some things simpler.

in this case i should put the firebase .json in the B4A folder and the IOS .json in the B4I folder, corect?

Yes (B4i\Files\Special)

I tried to move the app to B4XPages, and i get few errors-

1) the firebase service is not initialized. i thought it is becuse "starter" is not called in b4XPages. but it is called. i put the service "firebase messing" in the root folder. should i put it in another place?
2) i use method setinfo2 to react to the notification arrivel and click. it allowed me to pass data to the activity. how should i open the B4xPages Mainpage from the service? can it be done? can i pass info to it? it not, should i open the activity and then, from there, to open the mainpage?

3) can't i use #BridgeLogger: true from the mainpage?

1) It doesn't matter where you put the file.
I've prepared a small example of B4XPages with push: https://www.b4x.com/android/forum/threads/b4x-b4xpages-firebase-push-example.120523/#content

2) All the pages are inside the main activity. You should set the activity parameter to Main. You can get the notification tag in Activity_Resume in Main, and do whatever you need with it. Remember that the B4XPages are regular classes.

3) You should add it to the Main module.

Well, i couldn't find any different between your code and my own.

but i keep get error-
java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process b4a.example. Make sure to call FirebaseApp.initializeApp(Context) first.
do you have any idea?

OK. i solved it. i forgot to add the permission to the menifest in the new project.

thanks a lot.