can "rentals" on Adobe programs be cancelled?

If you get the month-to-month Photoshop plan at the higher price per month, you can cancel ANYTIME, no fee.  But Annual plans (prepaid or paid monthly) require a 12-month commitment.  See screenshot.

The 7 days is probably chosen to give enough time to make sure it installs, starts and basically runs on your computer, and has promise for the job you want to do.  DON'T FORGET to cancel the trial if it fails.

use the trial, but don't start it until you're ready to test all the features you want.

Read the system requirements BEFORE you subscribe.  Make sure your computer meets the minimum CPU & GPU requirements. Most Creative Cloud apps work on:

• Windows 11 (64-bit), Windows 10 versions 22H2, 21H2, 21H1;
• MacOS 13 (Ventura), 12 (Monterey), macOS 11 (Big Sur).

- https://helpx.adobe.com/creative-cloud/system-requirements.html
- https://helpx.adobe.com/photoshop/system-requirements.html
- https://helpx.adobe.com/photoshop/kb/photoshop-cc-gpu-card-faq.html

If you decide to cancel, you have 14 days in which to do so.  After that however, there is a 50% early termination fee.

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How do I Cancel my Subscription?
https://helpx.adobe.com/manage-account/using/cancel-subscription.html
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Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

Hope that helps.

You have a 7 day trial and if you cancel INSIDE 14 days you will receive a refund

Once you go past the 14 days your subscription is active and you pay a fee of 1/2 of the remaining time to cancel early