This site contains pretty much all the info you need: https://rollsafe.org/

Not if you follow all the harm reduction steps ;) Then you just have a lazy day or don’t even notice it.

You probably couldn’t game very much on a macbook. Maybe you could on the more expensive variants with Radeon Pro graphics, but those aren’t your typical gaming GPUs.

Also taking too much vitamin C can lead to kidney stones.

Maybe you mean this one: https://youtu.be/hGVVAQVdEOs?t=4m50s

where

That’s called Jamais vu, the opposite of Deja vu ;)