Ionic 3 vs 4 issues

I’m developing my app using Ionic 3, but I noticed that the newer version has been released so I want to ask few questions about the versions.

1.)Can I release my app on Google play and App store without any problems with version 3?

2.)Do I must upgrade version 3 to 4 for the future?(Is there any possibility that version 3 won’t work anymore in the future?)

3.)I have been finished development like 80% of total and I’m not making heavy app like games or something, will it be worth if I change version to 4 for me from now?

Yes.

You do not have to upgrade. But as new versions are released to resolve bugs and problems, it is of course theoretically possible that a super bad bug is foind that breaks your app. But it is really unprobable.

Yes, Ionic 4 is definitely worth upgrading to. It is faster and more convenient. But if you are already 80% done and don’t see any near problems with finishing your app, you can do so first and upgrade to Ionic 4 after you released your app and give it a nice speed and feature boost then.