Retina-only iPhone apps

I've got a few questions and I hope you could help me.

1. Are there any retina-only iphone apps? I mean apps that doesn't support iPhone 3GS and lower?

2. I read somewhere that Apple isn't accepting any iPhone app that doesn't support non-retina resolutions, is this true?

3. Lastly, how long do you think will Apple support non-retina apps?