We have made 3D GAINS available in every country that Apple App Store and Google Play Store would allow us to. To check if you can access the app, just visit the store on your device, search for "3D GAINS" and try downloading the app.
You can download 3D GAINS for free, however, to use the app you will need to purchase a subscription. Google Play Store is known to limit in-app purchases for certain locations so if you are an Android user you can check the information they provide about this matter here. Apple users usually have no issues of this nature, however, a similar list regarding Apple services available in different countries can be found here.