1. I got G Ranger and G Jug from grinding chapter 3 nightmare for a some time, I quit grinding chapter 3 nightmare after completing it for the 32nd time.
2. I got the beat chapter 4 nightmare badge first before the beat chapter 4 normal badge (proof is go to my profile and look at my badges, there you will see that I have gotten nightmare first before normal), however I got the nightmare first because of assistance from 3 other players however the normal I solo'ed it and then I have beaten nightmare solo.
Also fun fact, at wave 4 specifically after you have beaten corrupted apex predator and when there is some time left before it becomes wave 5 on chapter 4 normal solo, if you just spam a lot of top path g jugs and a few bottom g jugs to fill the circle and go afk, you will be guaranteed to win for some reason, trust me I was going dinner but before that I spammed a bunch of top and bottom paths of g jugs and once I finished dinner I saw the screen saying that I achieved victory lol.