After all can mean 'in spite of what was said before' or 'contrary to what was expected'. Position: usually at the end of a clause.
I 'm sorry. I know I said Iwould help you, but i can't after all. I expected to fail the exam, but I passed after all.
Another meaning is 'we mustn't forget that...', introducing an argument or reason which may have been forgotten. Positon: at the beginning or end of a clause.
Of course your're tried. After all, you were up all night. Let's finish the cake. Somebody's got to eat it, after all.
2. not used for 'finally'
After all does not mean 'finally', 'at last', 'in the end'.
After the theatre we had supper and went to a nightclub; then we finally went home. (Not... after all we went home.