Car seat safety

I realized as I was putting my son in his car seat the other day that there’s some things I don’t know. (Disclaimer I would never put my son in harms way, that’s why I’m asking)

1. Does it matter how the car seat handle is placed while I’m driving? Like does it matter if it’s up or down safety wise?

2. If someone is in the backseat with him can they feed him a bottle while he’s in the seat and I’m driving/the car is in motion?