Yes. We all need a certain amount of sleep per day. Even as adults, we know that a nap will make us go to bed later in the day. In a perfect world, we should have a good night's rest every night. The only way to answer your question is for you to try taking out the afternoon nap, and see if your baby will sleep at an earlier bed time and longer at night. If it doesn't help, let him/her nap.
Yes. There is a misconception that anyone sleeps "thru the night". Everyone goes thru sleep stages & with luck the transition doesn't bring you to full aleartness. Babies are capable of one 3-4 hr period of deep sleep/24hr & you can push that to late night/early am by never letting baby nap more than 2hrs during the day/eve. If baby is able to self settle to start the night, they can do so at 4am.