First day of SS, need some clarification please.

So today marks my first day of SS, and I just have a few questions for you lovely people of fittit. First of all, on a workout day, do you do 3x5 of each excercise (Minus DL), or warm-up to your weight, and then 2x5? Also, I decided to on my first day do Squats, Deadlifts, Bench Press, and 3 sets of pull-ups until failure (Also, what's the difference between chin-ups and pull-ups?), so seeing as that's my workout A, what should my workout B look like? Also, with regards to eating post-workout, how long should I wait after my workout to eat, and how much? Should I have a snack on my way home from the gym, if the earliest I could eat after the gym (snack not included) is approximately an hour?