Not under the 14 day right to cancel. The goods should be returned in as new condition so they can be resold.
If you’ve opened the box and turned it on, it’s not as new and the retailer has the right to charge you fee as they can only resell it as open box/b-grade. Many don’t but they could.
Ultimately it comes down to what’s reasonable to inspect the item so I’m most cases it’s reasonable for you to open the shipping box to look at the retail packaging to check it’s the right item or in the case of a T-shirt try it on.
But it’s not reasonable for you to bust open the retail packaging and test it out for 24 hours before deciding you want to cancel.
The 14 day right to cancel is intended to give you a similar experience to buying something in a retail shop, e.g. you get to pick up the retail packaging before you buy. You wouldn’t get to open the box and turn use the item before buying it.
Now if it doesn’t work or isn’t as described, that’s a different issue and has different rights.
The TLDR is, it’s not a 14 day free trial.
Retailers may offer terms which go over and above your statutory rights but don’t confuse them with your statutory rights. If you buy something face to face, you’ve actually got no statutory right to return it if you change your mind. Almost all retailers accept face to face returns if you change your mind but they would not take a return if you opened the box or used the item unless it was faulty.