In terms of diagnosis, I worked in education and had experience and I have several family member that show traits and it has negatively impacted their lives so I was always aware.
I started saving up when she was little as knew Secondary school could be expensive on the assumption that if she needed to we could go private / get braces / pay for expensive overseas school trips. She pretty much thrived at Primary and didn't struggle until Secondary when I was able to bypass the NHS 4 year waiting list and just went private. Never consulted the doctors, just informed school of my concerns they didn't recognize anything in her until after the fact. She never would have hit the bar to even be put forward for an NHS assessment because her autism is only an issue for her, she exhibits no challenging behaviour and not in MH crisis because we nipped it in the bud early
DD is extremely well behaved, loves rules, gets upset if she thinks someone has broken them, would punish herself with 'naughty' step despite it being something we never had. Never ever tantrummed (unless under the weather, tired or getting in the pushchair)
Appeared to roleplay with small world toys but actually it was a direct recreation of something she had experienced or seen via other media.
Games were always extremely complicated, a game of touch/tag had about 25 different rules
No issues with clothes but minor issues /preferences with food - whole banana/ melon great, sliced and 'slimy' melon/banana and absolute no go. Is noise sensitive and thinks hand dryers are the work of the devil. Doesn't like it hot and bright so we do lots of things early morning or in the evening
Only thing Primary school ever brought up was she liked to watch children rather than play with them but I brushed that off as she was an only child, and her teacher once called me because she wasn't writing at length in creative writing whereas her writing in other subjects was fantastic. She's well into her teens now, loves writing and language as a tool loves Shakespeare and writing her own poetry and reading play scripts and poetry. Hates creative writing and fiction novels with an absolute passion.
As part of her autism assessment they did a WISC V which was worth it's weight in gold and showed that her language and other academic skills put her in the extremely gifted range but her processing and working memory were 'just' average. So her ability had masked her disability through Primary where she didn't need to use any real effort on the academics but this made absolute perfect sense as she'll forget a list of instructions you give her, will do very complicated maths written down but still count on her fingers for mental arithmetic, same with spelling on paper and outloud.
Start of secondary school she had COVID badly a week in and took quite a while to recover, really struggled with the noise at school and unpredictability of other students and general school environment.
She becomes 'more' autistic when ill and tired so she feels everything more and it's harder to cope and she gets overwhelmed much easier. She rarely has meltdowns, but rather shuts down, loses the ability to speak and just goes into herself.
Year 7-8 was the worst time, I think hormones have settled now and she manages her environment much better so she can cope better with lots of downtime, noise cancelling headphones.