How to clear space on my iPhone 4 to update iOS 8?

I deleted all my apps and pics even my messages and phone log still won't let me update.

IOS 8 is not available for iPhone 4. It was only released for iPhone 4s and up.

Latest version for iPhone 4 is iOS 7.1.2. If you really want iOS 8 then you need to update your phone.

You can't update your iPhone 4 to iOS 8. You'll need to buy at least an iPhone 4S if you want it.

As I know, iOS 8 is not available for iPhone 4.

It's not the problem of space but the iPhone 4. IOS 8 doesn't support iPhone 4.