HOW IF I BUY STORAGE FOR A MONTH AND THAN CANCEL WILL ALL THE PHOTOS ETC SAVED TO ICLOUD DURING THE MONTH WILL BE SAVED FOREVER

Apple reserves the right to delete your data if you exceed the storage you have paid for.

https://www.apple.com/legal/internet-services/icloud/

The applicable storage fee for an upgraded storage plan will take effect immediately; downgrades to your storage plan will take effect on the next annual or monthly billing date. YOU ARE RESPONSIBLE FOR THE TIMELY PAYMENT OF ALL FEES AND FOR PROVIDING APPLE WITH VALID CREDIT CARD OR PAYMENT ACCOUNT DETAILS FOR PAYMENT OF ALL FEES. If Apple is unable to successfully charge your credit card or payment account for fees due, Apple reserves the right to revoke or restrict access to your stored Content, delete your stored Content, or terminate your Account. If you want to designate a different credit card or payment account or if there is a change in your credit card or payment account status, you must change your information online in the Account Information section of iCloud; this may temporarily disrupt your access to the Services while Apple verifies your new payment information. We may contact you via email regarding your account, for reasons including, without limitation, reaching or exceeding your storage limit. 

Click on the link to read how to "Downgrade or cancel your iCloud storage plan" on an iOS device, a Mac, or a PC. --> https://support.apple.com/HT207594

"What happens when you decrease your storage plan

When you downgrade your iCloud storage plan, the storage decrease takes effect after your current monthly or annual subscription ends.

If you downgrade or cancel your plan and your stored iCloud content exceeds your available storage, new photos and videos don’t upload to iCloud Photos, files don't upload in iCloud Drive, Messages in iCloud don't update, and your iOS devices don't back up. Learn how to manage your storage by deleting the information that you don't need anymore.

If you downgrade to the free iCloud Storage plan, you'll have 5GB of storage."

March 2021 post by ASC contributor Michael Black

https://discussions.apple.com/thread/252568292?answerId=254839872022#254839872022

- "When people cancel a subscription, they get an email saying they have 30 days to transfer their data for safe keeping, after which data will be purged to fit within 5GB."

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