Can you facetime on your iphone 4 using 3g?

I have a verizon plan. Iphone 4

I think you only can on iphone 5. I might be mistaken though.

Yes you can, but it will use your data plan. And it will use a lot of it.

You can, but only if you have IOS 6
(I have a 4s)

Yes you can if you've updated your iPhone's software to iOS Version 6

To Update your iOS Software:
Via iTunes:
1) Plug your iPhone into your computer with the Syncing cable
2) Open up iTunes
3) Look on the Devices tab on the left for your iPhone
4) Click on it and under Summary it should show the option to Update it

Via iPhone:
1) Go to Settings
2) Go to General
3) Go to Software Update

You can't. The iPhone 3G does not have a FaceTime camera, only an iSight, so it will not be able to send or receive FaceTime calls. An iPhone 4, 4S, or 5 will be able to FaceTime with all iOS devices with a FaceTime camera, or all Mac OS X computers with a FaceTime camera.

Yes you can. But, your iphone should be jailbroken. Youll need CYDIA and search for FACEBREAK.