Does the solution include semantic HTML?
Yes it does.
Is it accessible, and what improvements could be made?
The alt tag might need more clarification...i.e. what does a QR code do?
Does the layout look good on a range of screen sizes?
Yes it does.
Is the code well-structured, readable, and reusable?
I can't really comment to this as I am not a professional.
Does the solution differ considerably from the design?
In my opinion it does not differ greatly.