About the Ionic not being defined, using Ionic.io(); before declaring Ionic solved my problem. I got the pushNotification working with the ionic.io at last. 
Hey, this is @nani_madepalli i’m trying with this example, but i got an error like “MISSING_INSTANCEID_SERVICE”, please help me to solve the problem
Thanks in advance
You get this error because you didn’t updated your SDK with all the required package mentioned in the plugin documentation. Your emulator need the Google Play Services to be able to use this plugin.
Hi Devniz when you free you teach in online this concept.if any problem please reply Yes/No.Not only Devniz any body done this push Notification Please take a class with me because i am yours friend.
Thanks @Devniz
Just removed all the new Ionic.Push code and started using PushNotification.init.
I can now successfully use all the stuff which is here https://github.com/phonegap/phonegap-plugin-push/blob/master/docs/API.md#pushnotificationinitoptions
@Chacho Happy to hear that it worked for you ;D
@Chacho Hi,
Can you share your code with the plugin please ?