A.B.
Every child is different, but you can potty train any child, whether or not they are exhibiting "ready" signs. The key is patience and never being negative or upset about accidents.
Most people wait until kids can pull their own pants up and down, but that is because they don't want to potty train only to have to help the child go potty every time, anyway.
I trained my son by 21 months. I did have to take him to the potty every time, but I preferred that to keeping him in diapers, because older children can be much more stubborn. It is better for their skin to be out of diapers, too.
As for being dry all night, some kids wet the bed until they are 12, so that would be a long wait . . .