To "Request a refund for apps or content that you bought from Apple" click on this link --> https://support.apple.com/HT204084
If you have problems using that way, note the below:
The people responding on this support forum are users like you and we only know what Apple says in its documentation and what our own and other users' experience tells us. Apple does not have much on its criteria for refusing refunds. Here are two sections from the September, 2020 Apple Media Services Terms and Conditions - https://www.apple.com/legal/internet-services/itunes/us/terms.html
- "All Transactions are final."
I understand this as meaning Apple is starting from a point where any refund is considered an exception. They can simply say no without having to provide a reason.
- "From time to time, Apple may refuse a refund request if we find evidence of fraud, refund abuse, or other manipulative behavior that entitles Apple to a corresponding counterclaim."
You can see if the terms are different for where you live by clicking on this link https://www.apple.com/legal/internet-services/itunes/ select your location and then your language.
If you feel you want to discuss a refund request, try to contact a live person using a telephone or chat request.
Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world." Click here --> https://support.apple.com/HT201232
As for your topic question, Apple no longer includes a time limit in any of its documentation. In the past there was a nominal 90 day limit but I can no longer find. This document mentions a "refund period" but when you go to the Terms and Conditions document and search for "period" you do not get anything metioning a refund period.