Responsive card using Flexbox and Media Queries

I feel I have extensively and conveniently used Flexbox across this project.

Q1. Can any flexbox alternatives be more efficient in any of the scenarios? (Below is the list of places I used flexbox:

1. Alignment of Discounted and MRP prices.
2. Within the Call-to-action Button for the Icon and Text's Alignment.
3. In Desktop Design, Centering the Card Component vertically and horizontally.
4. In Desktop Design, Flexing Image and Description within card to Row direction.
5. In Desktop Design, Spacing a Column Flex of Card Description elements.)

Q2. Suggestions/Improvements to structure responsive bits in the code. (style.css)

Q3. I have not used img HTML elements for the Card image throughout this project, I used background-image CSS Rule instead, Will this impact SEO and Search results? And is my implementation considered as best practice in the industry?

Q4. Is there a more elegant way to Round corners of our divs, in this case. I had to repeat border-radius at 2 places, one for image div and the other for the card. Can this be improved?

Thanks for reviewing, in advance. Stay safe & take care :)