Is iMessges available for iPhone 3GS?

I have an iPhone 3GS and I was wondering if i could download iMessages onto it.
Can anyone help?
(No jailbreaks)

Added (1). I can't find it on the app store. Where is it? What do I type in?

Added (2). I have IOS 6.1.3

Downgrade ios 7.0.3 to 6.1.2 iphone 4s?

Hi guys i wanna downgrade my iphone 4s ios 7 to ios 6.1.2 but can i use other shsh bobles another iphone4s to my iphone 4s it is in ios 6.1.2. And it is iphone 4s Can i… Use the shsh to my iphone
So so sory for my english