OldClash is a private server for older Clash of Clans versions from 2015 to play on. This private server is mostly targeted to only older devices (can of course also be played on modern devices), such as iPod Touch 4's, iPhone 4's or Samsung Galaxy SIII's, etc.
OldClash has a mostly complete featureset, with the only major thing lacking being clan wars. Here's the full "works and doesn't work" list.
Here's some screenshots of the in-game experience in OldClash.
On IOS you can also just install the clients on-device. This requires AppSync Unified and is the easiest way to install OldClash. Don't trust any other site that provides OldClash clients, only get them from here.
Minimum required OS is iOS 4.3, on which only version 7.1.1 will work. Anything above will work with any version.
The installation process is more straightforward on android, simply download and install. Version 7.65 has been left out due to unfixable crashing issues.
Minimum required OS is Android 2.3