Strange thing to lie about, and opening with a lie makes it hard to believe anything else you say. ‘I chose my’, ‘DP bought me a”
did you wear it to go home or for a coffee?
Again I find it hard to believe that for three days you didn’t so much as want to look at it never mind wear it.
”all this bother” is somewhat dramatic, you found a scuff on a ring* the jeweller has offered to polish it, no drama. I had my naturally scratched engagement ring polished for my wedding day, it looked brand new.
you claim the shop was dimly lit, which is not true and despite a £2.5k ring being entry level for them you will have been given the utmost customer care and opportunity to inspect the ring before purchase.
you're comparing apples with oranges but regardless a shop is unlikely to offer a repair to a dress, secondly a lot of dresses are sold with visible non returnable if removed tags and thirdly with tags off it would be very down to the discretion of the shop.
your story doesn’t add up and I stand by the fact you or your DP either has buyers remorse or you regret damaging it, don’t want to admit that but want a shiny new one.
You need to admit to yourself that you’ve messed up and accept the jewellers kind offer
*a ring that you seem to not really care much about as either you didn’t look at it for three days or you’ve worn it carelessly.