I dont want my server to be spammed. Currently I am only in payment-related notifs (eg: user successfully renewed his subscription, user didnt successfully renew his subscriptions, ..) Where can I set that?

Is there an API Endpoint that I can call to check if user still have valid subscription? I want to be sure that his subscription renewal was succesful (ie: I dont want to give him another month/year/.. if his latest renewal wasnt successful) Would GET https://api.storekit.itunes.apple.com/inApps/v1/transactions/{transactionId} be the correct API endpoint to call? But I wonder, after subscription auto-renews, do we still use the same transactionId to check whether his subs is still valid?

After reading thru https://developer.apple.com/documentation/appstoreserverapi a million times, I cannot find anything that seems even remotely like the replacement for the deprecated https://developer.apple.com/documentation/appstorereceipts/verifyreceipt Please help.

Is there a way to make a subscription's auto-renewal fail in sandbox environment? Currently, I see no such options (screenshot)