Good day, we are developing an educational app for children. The essence of the application: the child gets access to the games only after passing various educational tasks. We plan to use accessibility services to restrict access to the device during the game.
Question: does the use of accessibility services in this application contradict Google's rules, and will it be allowed for distribution in google play?
Questions about Policy are best answered by looking at the Google Play Developer Policy centre, not on StackOverflow. This one doesn't seem well covered there. But in emails sent out to warn developers cited in the news, the emails say
Apps requesting accessibility services should only be used to help users with disabilities use Android devices and apps.
and
If you aren’t already doing so, you must explain to users how your app is using the ‘android.permission.BIND_ACCESSIBILITY_SERVICE’ to help users with disabilities use Android devices and apps. Apps that fail to meet this requirement within 30 days may be removed from Google Play
It doesn't sound like you are using it to help users with disabilities so it seems likely this won't be allowed.
You can always contact Google Play Console support using the help menu in the Play Console, which is accessed by the question mark "?" icon.