If the boy is at least 3 years old and the girl has been in heat then yes.
Absolutely. If they can physically mate, they can conceive.
If the size difference is too much, it is unlikely that the male will manage to get it right by himself. It would take artificial insemination by a vet to produce such an offspring.
The girl dog has puppies
Yes they can and it could end up killing the girl dog in the birthing process. The male should ALWAYS be smaller than the female.
A male dog will have an easily-located penis on his underside.