Yes you can make ADR's at 180 days out. The advantage for folk staying on site is that they can make ADR's 180 days out from date of check in, so basically they can make all their ADR's at the same 180 day mark (even if technically some are in fact 188 days out) This wasn't always the case for guests on site, I have called up every day to get my ADR's. So if you are offsite, and want to absolutely make sure you get your dining plans exact, you will need to call for each at 180 days out.
They do not need a confirmation number (only for those on site) They will want your home telephone number, that's all.