If it were as easy as that @Bigbenbube, a lot more parents would have a diagnosis much earlier in their child's life.
My DS's best friend is autistic. He was diagnosed at about 3 years old. He wasn't speaking when he started pre-school. He had speech therapy, went to the local primary and secondary with my DS and has now got a place in a local college doing engineering. He can now speak for England (you can't shut him up!) He's had to do resits in some exams as he found them hard, but passed 2nd time around. Job done. A pass is a pass.
The point is that there are varying degrees of autism. My DS's other friend is also autistic, passed all her GCSEs with grade 6 or above (2 grade 9's). She doesn't like too much noise and has learned to 'build up her reserves' if there's a school prom or party - she'll have a quiet day the day before. It works for her and her friends respect that so arrange things around it. No one can say 'an autistic child will be like this' under every circumstance. Autism doesn't work like that.
DS was a quiet baby...except at night when he woke every four hours! During the day he was alert but giggly rather than crying. Not autistic to my knowledge.
As far as interaction is concerned. I just had him in his chair in the kitchen when I was cooking. I may have chatted about what I was doing or I may have had the radio on and been singing along (or arguing with someone on the radio if it was a chatshow). We'd have a story every day. Didn't matter what it was (my friend used to read to her kids pieces from the newspaper as she got bored with kids books sometimes - prolific readers now).
We'd also have the TV on for a while as I needed a break! Sometimes for the whole day when I just wasn't in 'mummy entertaining' mood. Sometimes kids TV but I used to have a cup of tea every day whilst watching old 'Murder she Wrote' programmes (there's only so much rhyme time you can cope with even on a good day!) My DS used to sing the theme tune when he was a toddler - I may have had that on rather TOO much (ha ha!)
As he grew older we'd do his train set, go to the park, do obstacle courses with old boxes, do craft stuff and go to toddler groups a couple of times a week - he met his best friend when they were on a mat together at 6 months old!
I'd always tell him what I was doing to him - 'let's change your nappy, I'm just going to lift your legs up, time to get you cleaned up'. It's chatter and I just feel it's nice to tell them what you're going to do! And DH and I would little games like finger walking up DS's tummy and going 'boo' when his nappy was off.
You're doing just fine - please don't get caught up on 'I must do three hours interaction every day'. You're not a machine - you're a mum. Talk is talk. Your child likes your voice - they don't care if you're talking about cutting up carrots or doing a specific chatty game. They have no idea of the difference. Showing your DC the bubbles in your washing up water (blowing them gently to show them moving is a good trick) is interaction just the same as doing bubble blowing games.