The documentation says that an app can ask a User three times per year via SKSToreReviewController to place a rating.
Most suggest to save a variable in UserDefaults and call the function after a couple of uses. What happens if you call the function more than three times per year? Will the App Store just ignore the calls and after a year asks for a rating again or will you get some kind of error?
And what happens if the app has been updated (ie. a jump from version 1.0 to version 2.0)? Will the 3 requests be reset?
In short, you choose the appropriate time to display the alert, but the system will decide whether to actually show the alert or not. So don't worry about "over-calling" as long as you don't call it as a response to user interaction.
Although you should call this method when it makes sense in the user experience flow of your app, the actual display of a rating/review request view is governed by App Store policy. Because this method may or may not present an alert, it's not appropriate to call it in response to a button tap or other user action.
Highlight mine.
https://developer.apple.com/documentation/storekit/skstorereviewcontroller/2851536-requestreview
As for your second question, the only reference I can find regarding how many times it might be displayed is "3 times per year". It doesn't mention 3 times per app version or update. Use this API wisely.