Where there is a will there is a way! HA has come a long ways in the short time I have been using it! With the constant updates and this kick @$$ community you will surely achieve your goals and then some! So dive in and welcome to HA!
You haven’t indicated if you want to DIY everything or buy.
1 multi room audio.
You could look at using Logitech squeezebox on raspberry Pi’s. Plenty of guides around on how to do it and you can control it from HA.
Sonos just works but it more expensive.
2, the ip cameras. There are plenty of options out there but I would start by looking at hikvision or dahua ip cameras. Both of these have MJPEG streams that HA supports.
I have hikvision cameras myself.
3 PIR. I think mysensors do some arduino based PIR sensors.
You could use zwave if you want to got that way.
4 power outlets. Does it have to be 433hz? There are plenty of off the shelf products such as WeMo, orvibo and sonoff to name a few of the top of my head.