Hi and welcome.
The official rule is that you can book ADRs 180 days before you need them.
BUT if you stay at a Disney resort, they change it a bit: you still have to wait until 180 days before you arrive. But, when you hit that 180 day mark, you can make up to 10 days worth of reservations at once. (As opposed to calling each day, 180 days before you need a particular reservation.)
The
DDP is the more basic plan: 1 snack, 1 counter service and 1 table service meal per day. There's also a more comprehensive plan that offers more for a higher cost.
I'm not sure on the DDE.... wati, I looked it up:
"Become a member in the Disney Dining Experience program for $60.00 and add a second membership for your spouse or partner for $25.00.
The Disney Dining Experience gives you:
20% off of food and beverages at over 70 Disney Resort hotel and Theme Park RESTAURANTS. (Discount is good for up to 10 guests.)
Theme Park and Resort parking for dining purposes
Member-Only invitations to exclusive events
Half Price admission at Pleasure Island for DDE member
Free Admission to Boardwalk's Atlantic Dance for DDE member and guest
Annual Passholders can join up by calling 407-566-5858 (Mon-Fri, 9:00am to 6

m EST). The Disney Dining Experience is not accepted during holidays, including New Year's Eve, New Year's Day, Easter, Mother's Day, July 4, Thanksgiving, Christmas Eve and Christmas Day. Please allow 2 to 3 weeks for processing. NOTE: If you order your card and it doesn't arrive before you leave for WDW, you can pick up a temporary voucher at Epcot's Guest Relations. "