Q: I need to download skype to iPhone 4 and when I start to download and install it the program say the softwere must be more than 8 and the iPhone 4 softwere is 7.1.2 and I tray to update the iPhone 4 but the iPhone say that the softwere is not need

Try the procedure on this page: https://support.apple.com/en-us/HT201377

However, in order to do this, the vendor must provide a version of the app compatible with your version of iOS. It is not clear Microsoft does for Skype.

You will only be offered to download an older version, if you have installed Skype before on the account you use for the App Store. A workaround is to log in with that account on iTunes on a PC or Mac, and "buy" Skype from the store there. Then you can install the older version from the phone's App Store.