The iPhone 4 model isn’t compatible with iOS versions newer than 7.1, so while you couldnt update it to 9.1 (or newer) you can install the most recent system update available (7.1) by connecting your phone via usb cord to a computer running iTunes
JAMJEN76, thank you for reaching out to us today. I can understand wanting to update the software on your iPhone 4. I do not believe that this is good idea based on the age of your phone. The phone just does not have enough memory to take such a large update.
It might be time to think about upgrading your phone.
You can still try but be warned this might not provide the performance that you are looking for.
Follow the link for more information on how to do the update: http://spr.ly/6580DMSDa;
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