How does someone check if an Apple device is suitable for playing a game a developed. I realised that in some cases, the devices that are 3 years old have too humble performance and my games have a lag because of that. Is there a test I can run to determine if my app can be played on for example iPad3 or iphone 5.
The only way to tell is to run it on that device. Apple has made a few of these options better by allowing you to test things with Xcode server, unfortunately most of the time it has to be done manually.
It's also worth noting that you could optimize for older devices by making changes to the game such as lowering textures, particle effects, shaders and more.