About license to buy

I doubt that you will be allowed to distribute the file commercially or for free, even modified with minor changes only.

You could sell mugs, t-shirts and posters, however, with your image printed on if you take an extended licence. You can't take an extended licence for premium assets, however.

Extended licenses

With an Extended license, you may:

• Use the asset with all the rights granted in the Standard license.
• Reproduce the asset beyond the 500,000 copy/viewer restriction.
• Create merchandise or products for resale or distribution where the main value of the product is associated with the asset itself, such as a coffee mug or t-shirt.

With an Extended license, you may not:

• Distribute the stand-alone file.

Licences are perpetual.

The copyright to the image stays with the original creator. The creator agreed that Adobe can sell licences of the asset, but they did not cede ownership of the creation. Any modification you apply is owned by yourself.

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).

From this page:

https://stock.adobe.com/license-terms

"you may not:

• Create merchandise, templates, or other products for resale or distribution where the primary value of the product is associated with the asset itself. For example, you can't use the asset to create a poster, t-shirt, or coffee mug that someone would buy specifically because of the asset printed on it."

From your statement of intended purpose, it seems that the primary value of the backgrounds that you intend to sell is the licensed image with some minor modification. This is clearly in violation of the license terms.