Open Google Play, touch your Profile icon (top right) > Manage apps and device > Updates available, look for iReal Pro.

 

Specifications

Play store > iReal Pro > About this app > App info should show specifications, minimum required Android OS etc.

 

We currently offer free updates but as your device gets older you might not be able to install the very latest version with the newest features.

Also, make sure you always update your device to the latest available version of Android.