Jonesella - NO! Not poisonous. They will bite if you pick them up wrong, and it hurts, but they have no venom. Racers eat rodents and insects and small birds. Good things to have around your landscape. Not so good around a chicken coop if you have tiny chicks, but you can use screens and keep them out until the chicks are bigger.

That is a baby ratsnake (Pantherophis obsoletus). Completely harmless rodent eaters.

I assume that is a captive snake (or an escaped captive). While the pattern and coloration might first suggest that it is a striped morph California Kingsnake (Lampropeltis getula), the head shape and pattern tells a different story. The head shape looks to me like that of a milksnake (Lampropeltis triangulum). Therefore I am pretty sure this is one of the captive hybrids between a Cal King and a Milksnake.

Appears to be an anerythristic corn snake. Quite common...who ever had the snake should know that and have further information for you.