I Would Like To Try iOS 8 Beta 2 On My Iphone 4s?

But i'm worried that my warranty will be gone but a friend of mine did it and he told me that he still has his cause he never reported that he jailbroke his phone and his warranty is still good because of a time limit T Mobile Told Him I talked to apple they told me it does void the warranty

You can, but the moment you reboot your phone it will ask for the UDID.

Search on Youtube how to install iOS8 on your iPhone. You'll have to download the right version of IOS. If you don't, it won't work.

You can't unless you register your UDID.

It's fine as long as you install register your device's UDID with a developer account through a site like http://www.udid.in/. It's $5, and then you don't need to worry about Apple disabling your device for running unreleased software.

Just register your UDID with a dev account using a site such as http://ios5activations.com/

If you don't register the UDID the phone will not activate after installing an iOS beta.