Your question is very vague and therefore hard to understand but I would assume you are asking for the explanation of the pun.
This phrase is a pun because skiers ski down slopes, and going down hill is another way of saying not going very well. Old skiers never die, they just go down hill is a pun because skiers go down hills.
The audience that doesn't exist.
I think its either logos or pathos :/ im not sure but its one of those 2
