[Jerrytheclown]

So I'm (hopefully) going to very shortly be buying my first bike. I've got all my gear ready and a permit as well as an MSF course under my belt but I still absolutely do not feel confident enough in my own abilities to ride around surface streets with traffic right now. I intend to practice a bunch around parking lots and in a nearby neighborhood but I was wondering what kind of stuff I should work on?

Also, there's a lot of conflicting info flying around the internet so I have a few random questions about specific stuff I've read about.
1) Am I supposed to downshift when I turn? How about when I stop? During MSF, they never told us to shift at all during turns but they did tell us to always hold the clutch and shift down into first before stopping.
2) Is there some kind of guideline for optimal RPM to MPH conversion for the Ninja 250r specifically? Like, how do I know what gear I should be in at a given speed? In MSF we never went over third gear or 20MPH, what should I expect to top out at riding 30-40MPH surface streets?
3) The place where I live has a lot of hills and stop signs on those hills. Having ridden in people's manual transmission cars and watched then do the crazy feet dance to avoid letting the car slide or stall, I'm guessing stopping and starting uphill is a pain in the butt for motorcycles as well? Any tips for this?
4)What is engine braking, really? I understood that it was a thing enough to pass the test but I have no idea what it really is beyond using the engine resistance to slow the bike. But how do I do it? Should I even bother? Is there any reason I would do it over just using the brakes?
5) How much traction does bike really have? In MSF they really hammered home traction as a limited resource but I obviously never had to put that to the test, so I have no feel for i. In a lot of motorcycle fail videos online, you'll see the rider lean to far over or something and the bike will just slide out from under them. Is that something that is easy to do? Should I be very mindful of not over-leaning?
6) Back during the course, my bike CONSTANTLY stalled. I feel like it might partially be because it was a beat up training bike but I was probably doing something wrong too. I was having a lot of trouble with the clutch because the friction zone felt really really narrow. Are all 250r's like that? If so, how do I manage it?

Ok phew. I think that's all the questions I have for now. Sorry for the wall of noob questions haha. I just don't want to be on the bike and not know what to do if something comes up. Thanks!