It's genuinely different for every child. For example, DD2 can't cope with surprises. For her birthday this year (13) I discussed it with her and she asked that everything was put in one bag, unwrapped. She knew what every present was, and wanted to watch me pack them into the bag. Then the next day, on her birthday, she very happily received her presents, one by one, unwrapped.
DD2 gets 'peopled out' extremely fast. She was in tears because we had arranged to have lunch with my parents, then DH mentioned that her grandparents abroad would probably like a Zoom call, then my sister decided that she needed to see DD2 on her birthday. DD2 was in floods of tears because all she had planned was visiting my parents for lunch.
DD2 is extremely shy. I wanted to go out for breakfast today, but she pointed out that the place we were going to is always busy. She said she'd rather stay home and have cereal. She then said that she wanted breakfast at the place, but couldn't cope with the number of people. In the end, she was reassured by the explanation that social distancing means less tables.
I have found that it's getting better as she gets older, because she can send me text messages to tell me what a problem is, or explain it, which means that we have less meltdowns.
The hardest part of getting assessed was the referral process. Once I bit the bullet and referred myself, the process was quite quick because it was so clear to them that she has ASD. She was on the list for 2 years, but we actually only had 2 appointments - the initial 'chat' appointment, and the formal assessment. They skipped all the other appointments because there was so much evidence on the referral form and her presentation was so clear to the worker we saw.