Like margarine or lard, when stored in fridge it's hard, a salted spread, works best on bread, but also goes with pasta

I'm dead? I'm not! What do? I Rot! I run around, dumb and strong. You bash my head with rock! Unless you want your brain be mine, consider self as murder swine!

You can cook noodles in me, or cook brain cells smoking me.

I have a skin but no scales, a stone but no heart, and though I am often purple, I was once a tiny white flower. If you dry me out, I change my name entirely. What am I?

When out in public and needing to wee, Please give me some ...