You can cancel your subscription yourself https://support.google.com/googleplay/answer/7018481
Unfortunately, there is only a version for Android. Versions for other platforms are planned.
Yes you can, you can help translate the app into your language. All phrases for translation are stored at link.
The app supports all methods allowed by Google. For more information, visit the website https://support.google.com/googleplay/answer/2651410.