Need help with mod character perks

[peppermintfrog]

I'm a newbie to modding and I'd like some help with the following character perks:

Character doesn't lose sanity in caves;

eating mushrooms gives double the hunger,sanity and health;

making a custom hat (that functions like a berry bush hat);

and how to make certain mobs passive to the character;

Also in what file do I need to put the coding related to perks?

(I'm using the extended character sample) 

 

thanks to anyone who decides to help!