I didn't want to read and run. I have a child with autism and they behaved like this when they were younger. If you're concerned there's a developmental issue, start the assessment process as soon as you can. I'm surprised the HV check around 2 1/2 didn't raise some flags. The early years help and a specialist nursery where the most help for us. It may just be pushing boundaries, who knows.
As a positive, the smearing of poo and urinating on the floor were a phase she's grown out of now. It was very much sensory seeking.
We have 'baby proofed' the house as much as possible (secured front door, cupboard locks, knifes locked away) but an adult will always be downstairs with them. We've had floods from taps, close calls with the toaster, escaping down the road)
Things to try for now..don't worry about limiting screen time, have sensory toys available ie. Trampoline, playdoh, kinetic sand, indoor swing, you can try compression sheets or weighted blankets, snooze next to them if you can, music, audiobooks, cartoons and please ask for help where you can.