Can anyone explain if there are any restrictions/limits on the menu items you can order?
Are there any other restrictions? Which restaurants do not accept
DDP?
There are very few restrictions on the DDP. Appetizers and desserts made for two people are excluded (unless you have two people order them

), specialty drinks that have the glow ice cubes or character straws clipped on them, if you order the Marrakesh feasts then you don't have a choice on the dessert (they give you a sampler plate of baklava), at the Morrocan CS they automatically give you a certain kind of baklava, and at the Pepper Market at CSR only Tier 1 and Tier 2 desserts are allowed. Those are the only limits I can think of. No alcoholic beverages, of course. Most places you can get milkshakes, smoothies, and flavored sodas and lemonade for your beverage, if you want them.
Restaurants that do not accept the DDP are the Bistro upstairs in France, Victoria and Alberts at the GF, the restaurants at the Swan and Dolphin, and Bongos, Fulton's, Portobello Yacht Club, House of Blues at DTD, and Rainforest Cafe at either DTD or AK. Those are the only ones I can think of that don't take it. We've used the DDP multiple times and have never had problems finding a restaurant that takes it.
One warning, both Beaches and Cream at the BC and the Plaza Restaurant at MK are priced like CS, but are definitely TS. They have good food, but are sort of a waste on the DDP.