There's no age limit to be left alone or stay home alone overnight in Canada except for two provinces which are New Brunswick and Manitoba Canada which states that by law your child must be at least 12 or older to be left alone overnight or for a length of time without provision making for adequate supervision.
A child cannot live by themselves as they would not be able to survive on their own or provide for themselves.
As a parent you're responsible for your child until they are 18 years of age and until they are at least 18 you can legally keep them at home and they would be considered a run away if they left your house before then.
Kids should not be left alone by themselves longer than an hour or so depending on their age although if they are above 10 to 12 then they can be left alone longer.
Babies however and toddlers should never be left alone nor should a child under the age of 8.
You cannot leave a baby or toddler at home sleeping while you're away.
A baby is a helpless little person that cannot fend for themselves or would not be able to get out of danger if the need arises.
For example lets say you left your baby at home by itself sleeping for just a few minutes and while you were gone your house caught fire?
The baby could not get up and get out of the house or call 911 and would die and then you would be charged and arrested.
It's illegal and child neglect to leave young children and babies home alone and you should never do so in the first place.
Always take your baby or young child with you even when they are sleeping.
I would never leave my baby at home by itself and if I did need to leave I would have a trusted adult watch them if I could not take them with me.
Once a child is 8 to 9 years old they can usually be left alone for short periods but not for too long.
I remember reading a news article online where a baby was killed in a house fire while the parents left and the house caught on fire.
Either way babies should never be left alone.
However you can step outside while the baby is sleeping but never actually leave the property and always check back in on the baby.