No, because you are not available and the company may ask you to work during the week.
No I wouldn't bother go somewhere else
Work for the weekends but don't settle there. I would definitely recommend looking for other jobs as well. Supermarket jobs are great for students - they can be long term, consistent in terms of hours, offer pay rises and prospects of moving up in the company (none of these of which you would get at Smiggle)
No you need to be fully flexible