How to upgrade to ios 7 in iPhone 4?

I have iPhone 4 and i'm from india. I'm so excited about ios 7.

When would i get ios 7 on myPhone? I'm on ios 6.0 (jailbreak). Yesterday i tried to update and it showed 6.1.3

Ios 7 is already released. How m i suppose to get it?

And which good ios 7 features will not support in iPhone 4?

Thanks !