Little complicated but standart topic

So back when i got my nexus 4 with a stock 4.2(or 4.2.x) The first thing I did was to root it with, im pretty sure i used this guide

Now im pretty sure that after 4.3 came out i didnt do the steps to root it back, I might have though, and i wasnt sure on the status of my custom recovery either(nor the bootloader), now please forgive my ignorance for forgetting what exactly the bootloader is and what does unlocking it provide on the technical level.

Anyway my phone works well, with 4.4.2 installed, problem is i need it rooted, now i try to launch SU but it tells me there was a problem and it might have something with 4.3 . So before going here i tried to to launch custom recovery, but it says "no command" there, now im a little worried.
I might be left without a recovery.

The phone launches normally though.
As it stands the issue might be a little over my head, and I not sure on how to approach the whole situation as it seems a little complicated.
So an explanation on what have might have happened with all the nexus updates, and a clarification if its safe to flash a custom recovery the normal way? And how do i proceed to reroot the device from there(since im aware its a different matter than rooting from scratch).

Thanks in advance and hope I didnt miss anything i could do for myself before asking here.