Shared Apple Id

If I sign in on 2 devices with the same Apple ID will all my apps, music, iMessages and mail be on both phones?

Yes, iCloud will synchronise your content and data to all your devices signed into your account.

Set up iCloud on all your devices tells you:

To set up iCloud on your devices, sign in to each of them with the same Apple ID and password. You can choose which apps store information in iCloud and which iCloud features you’re using separately on each device. Learn more about how each app or feature uses iCloud.

Note: When you turn off iCloud for an app or feature on a device, information stored in iCloud for that app or feature is no longer available on that device. However, it’s still available on other devices where iCloud is turned on for the app or feature. See How iCloud keeps information up to date across all your devices.

There may be a slight delay in syncing iCloud because new data needs to get uploaded and then downloaded on the other device.

FaceTime should ring at the same time.