Autism Spectrum Disorder is just that; a spectrum. Its not a straight line from 'not autistic' to 'very autistic', it's a vibrant colour palette of characteristics that a person with ASD may or may not have, including social differences, Language differences, sensory differences and repetitive behaviors. Some traits create difficulties in everyday life, and some traits can be very useful.
You can't diagnose Autism Spectrum Disorder from an Instagram post, but it's good to be aware of SOME of the things you might observe and think about if your intuition tells you your child is a little different. A child doesn't need to have all or even most of the ones I've listed, these are just some common ones.
All children will display one of these traits at some point. If you have a picky eater or your child sometimes likes to play alone, it's not cause for panic. To be diagnosed with Autism Spectrum Disorder, a child must display differences in each of these quadrants persistently. If you have concerns, write them down and come back to them in a couple of months. Have things changed or improved? If not - think about checking in with your GP.
We care about our children fiercely so it's scary if we think their development isn't tracking as expected. Just know that children with Autism Spectrum Disorder can be amazing, smart, cheeky, loveable, funny, inquisitive, interesting, awesome kids and there's lots of support out there to support your little one to develop on their own trajectory.