Can you lock a dementia person in their home?

No.

If someone is in the home with them, then yes you can lock them in. I used child safety knob covers so my Mom couldn't get out.

But for several hours because ur working or overnight no. This is a fire hazard.

If its gotten this far, and no one can be with the person 24/7, its time for an AL or LTC. If they need to be locked in and its done for several hours, that could be considered abuse and APS should be called in.

If you are there too, yes of course you can lock the front door. If the resident is alone, no you can't.

No.

No, if it seems the person needs to be locked, they need constant care, either 24/7 home care or a facility where there is always someone there.

Not without taking huge risks. Imagine if they hurt themselves, if there was an accident, fire, etc. Also, legal liabilities, the list goes on...