Does the refresh token expires when it is not used for long time?
@shashank-cognitica Здравко is correct; refresh tokens don't expire automatically or due to not using the refresh token. They can be revoked on demand though, or become invalid if the account itself is disabled, etc.
You can find more information on refresh tokens in the following resources:
@shashank-cognitica wrote: Does the refresh token expires when it is not used for long time?
No, it doesn't expire; or at least until you revoke it through your application or user disables it using the account settings; or account is disabled/deleted.