As I've read in below stack-overflow post and many another post that push will work fine after App transfer. like this post show:
will push notification still work after ownership transfer in iTunesConnect
But my question is suppose, I need to create an app Update for Transferred App(which I got from another developer account by transfer process), do I need to create new push certificates before app update, need to create a new one before submitting an app Update?
Note: I've used FCM for push notification. Please clear my doubts also it will be a great help, if you provide me some links about this information, which I don't know(App Update after App transfer to the new account).
No, you won't need to create a new APNS certificate for an app update.
The certificate is hosted on the server handling push notifications and that can be changed at any time. Keep a note of when the current certificate will expire and create a new one and replace it on the server before then.
If you don't know when the current APNS certificate expires, there's no hard in creating a new one now.