We submitted our app for review on 11th and it has been around 5 days , The status is still in review state . How long it will take to complete the review for the first release ?

We are developing new iOS app. To support some features in our app, we need to track whether the user has uninstalled the app or not. We are using silent push notification to track that similar to all 3rd party apps like appsflyer,adjust,braze etc We read about  Background pushes will only be delivered if the app has been used in the foreground in the past few weeks. (79379996) We want to know whether this feature has been already released in iOS 15 Whether the background or silent push will be delivered even if the app is not used for long ?