ADR for HS Timing and JTA?

I just secured an 8:45 am ADR for Hollywood & Vine on Friday October 17. Park opening is 9:00 am that day. What time will they allow us to enter for our reservation? Will I be able to sign up for JTA then as well or will I have to wait?

I don’t know the current procedure, but in February, we had an 8 o’clock ADR on a 9 o’clock open day. We arrived at 7:45, walked into the park and they were already accepting JTA sign ups. We signed up with no wait, and were at our reservation by 8 o’clock. As this ridiculous JTA issue was stressing me out more than any other aspect of our trip, this day turned out to be the most magical pixie-dust-sprinkled day we had!

Most reports I have read echo what @rebeecky mentioned above. Although, it seems that it can vary, the majority of people seem to be saying that if you have a pre-rd ADR, you should be able to sign up for JTA with ease and have the pick of show times.