Missions & Complexes

You don't need a BS for a level 4. It does make it a lot easier if you have low skills though...

Generally it's easier to work for one Faction at a time. However, it's not to bad if you work for multiple Corporations within said one Faction.

As for and back to the missions. Some level 4's are very very easy to do. Some you can do in a T2 cruiser or Frigate if you know what's what. Of course some are a tad insane if you're just starting out.
If you have a slow SP or don't know the missions, then the BS sized ships give you a bigger buffer and so a little more room for error.

You'll probably lose a few ships before you get it figured out though, everyone does :)

Edit - OP: posting twice can be an accident, but 6 times...?

No worries about all the topics.

Although when doing missions I found it a good idea to focus on one corporation per faction. This will keep your Loyalty Point pool centralized and keep you from switching stations often. Although if you like to chain missions, by accepting several at a time, then it won't hurt to hit all the corporations in your home system!

Then I would switch factions about every month or so due to standings. It isn't the end of the world if your standings get too low as you can fix that with skills and even running low sec L1 missions. If you want to freely move around high sec without worrying about the local Faction Navy breathing down your neck, try to keep them happy and do some missions for them every now and then!

Indeed, make a few friends. When I was first starting out all those years ago, I remember teaming up with a few guys I chatted with in the noob npc corp I was in. We'd group together each evening and try our hand at lvl4's in our poorly fitted/skilled BC's. Sometimes we'd die, sometimes we'd succeed but we had fun either way. I flew with that group of guys for my first year of playing and I still chat with them periodically. So just ask around in your npc corp's chat, unless you're a complete tool you shouldn't have any problems finding a few guys to fly and die gloriously with.

You're far too paranoid, very few would waste their time to suicide gank a t1 fitted BC just for the lols. Beyond that there is no mechanic that allows for it. NPC corps can't be war dec'd, if in fleet you don't get flagged for taking cans from someone within the fleet and so on. You simply can't get flagged and even if you do something that would flag you, you'll get a warning pop up before you do it. Noobs fleeting other noobs in the NPC starter corp is pretty safe I think.

If you get stuck, ask for help in local. I have helped many a player who has asked for help, and I am sure there are many who do.