1) You don’t need to defeat Margit and Godrick to get to the area north of Stormveil Castle, you can go all the way around using the path off to the right coming up the hill from Stormhill Shack and loop around to Lake of Liurnia.
2) Some people have been able to acquire the weapon even after killing Yura early on, as they apparently find him dying in the church when they eventually reach it. This means that you may not be locked out of getting the weapon if you decide to kill him early, but I don’t know the exact reasoning or steps if you choose to go this route.
3) Some people have told me they have been able to progress his storyline without killing the dragon in the lake. If this is the case then skip that step, and if the red summoning sign doesn’t spawn on the bridge, then go back and kill the dragon to make sure.
4) I only showed it briefly, but the stats page for the weapon is at 7:22
