App issues
OK I have Iphone4, you can not update or upgrade to IOS8 but most Apps require IOS8 in order to download. How do you get those apps to download?
iPhone 4, iOS 7.1.2
Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support
However, many app vendors do not extend support back. That is a vendor decision, not Apple's. The 4 is getting a little long in the tooth for tech devices. May be time to consider a new phone.