Hello,
Just after a bit of perspective.
I have two children, girls, age 5 and 3. My eldest was diagnosed with autism at 3 so I don't really have a benchmark for 'normal' behaviour in 3 year olds. She couldn't speak at all until she was 2.5, then it came in paragraphs (and she hasn't stopped talking since). Eldest is extremely high functioning (I hate that phrase and appreciate that it doesn't mean she doesn't struggle, but am using for the purposes of you understanding what I mean easily). As in she's verbal, no learning difficulties (she's advanced academically) but always struggled socially. She still does, she has an EHCP in mainstream school.
Anyway, my (just) 3 year old. She does not struggle in the same way as her sister did, or at all really. She spoke at 1, and quickly progressed with it, her speech from a young age was amazing. She's very happily sociable, mixes easily, loves preschool (not a single tear or wobble at drop off from her first day) and is beautifully behaved and compliant there she's never even been told off there!
She does have some autistic traits - she tiptoe walks sometimes, she is very restrictive and repetitive with food, she sorts toys (but does also play 'normally' and is good with imaginative play using small world toys etc), she recites short books like The Hungry Caterpillar from memory and has since she was 2, she's already starting to sound out phonics and can read some 3 letter words (since joining in with reception homeschooling earlier this year, I didn't 'teach' her this on purpose) and counts brilliantly. She subitizes too, up to 6, again because she joined in homeschooling.
But generally I don't - or didn't - have any massive concerns about autism.
However. Her tantrums! They are extreme. My eldest never did this, she has meltdowns that in hindsight were due to sensory overload etc (something we still deal with) but nothing like this at this age.
Youngest will go absolutely wild if she doesn't get her own way, isn't allowed to do something for herself that she wants to do. I'm quite chilled about letting her be independent with getting dressed etc, but she's not allowed to take her dinner out of the oven, much to her disgust!. If she loses a game, decides on this occasion she doesn't want to share, basically if anything displeases her or she is asked to do anything she doesn't want to.
She will scream and scream excessively and hysterically for an hour or more. She will hit and kick. She will say I've hurt her (when I haven't, I will maybe have picked her up to move her away from a situation or sit her somewhere else but I never, ever hurt her!) . She will throw things. Last night she actually tantrummed herself to sleep because her Dad refused to read her five bedtime stores (a random demand - she'd had her usual one each from us!).
Is this normal? On the one hand I'm worried about autism and thinking perhaps she is affected, I need to get her checked and just presents very differently to her sister. On the other I'm thinking this is perhaps what NT 3 year olds are like and that this is just standard 3 year old behaviour that I need to handle differently to how I would a meltdown, as in with appropriate discipline not other strategies which were better for my eldest.
She really is an absolute delight, half the time. The other half she's like a violently tempered tyrant!