We have a brand new Dairy Queen building near me but, I have never been in there.
I looked on line to see what type of Sundae's they have as well as all the DQ's in my area. (we have several)
They do sell Turtle Blizzards, but no Turtle Sundaes. You can customize a caramel or chocolate one to add nuts, another flavored topping, whipped cream and a cherry.
DQ is a franchise. Their menu offerings are what corporate determines. Individual stores cannot go rogue and add things to their menu.
And yes, they do charge for each thing added separately.