Yes, but it is way way back (probably over 300 million years ago).
yes they do in facts share a common ancestor.
An ancestor.
There has been no evidence of such an ancestor.
Yes these two share common ancestors.
Only if you share a common ancestor. This is seldom the case. Technically, there is no relationship.
no, but they share a common reptile ancestor.
that we share a common ancestor
Descendant organisms are organisms that share many in common because they share a common ancestor.
It will depend on whether or not you share a common ancestor. They could also be second cousins, if you all share a Great Grandparent. If you do not share a common ancestor, there is no relationship between you.
Crocodiles and birds share a common ancestor. This can be seen by comparing the internal anatomy of the two. Dogs and Dolphins also have a common ancestor. Their skeletons again are both distinctly mammillian. The ancestor of dogs and dolphins and the ancestor of birds and crocodiles will again share a common ancestor, but you will need to go much further back. I am not sure of the timescales but we are talking tens to hundreds of million years.
There is no relationship, you do not share a common ancestor.
They share a common ancestor.