The dogs got off the car by itself.
themselves
She didn't walked by herself.
walk
They swam by themself.
themselves
I walked to school by my self.
myself
He didn't did laundry by himself.
do
She ate lunch by herself.
didn't eat
You bought groceries by yourself.
yourselves
The hamster chop vegetables by itself.
chopped
It take a bus by itself.
took
He didn't washed his hair by himself.
wash
He cook by himself.
cooked
She stayed at home by herself
period (.)