yes it is.
Probaly but Casen is way cooler than Devin
Leo the cool lion that's cool
The nickname of "The personification of cool" was given to James Dean.
I think a cool nickname for Madlyn would be Maddie, or you could even use Lyn as your nickname. Maddie is a more casual nickname while Lyn is a little more formal, so it depends on what type of nickname you want to have.
Yes, many people call her 'Chezza'. What a cool nickname.