Newgrounds is far stricter with copyright due to the fact that it isn't really making any money besides just from people paying for supporter roles nowadays and it is far smaller than it used to be so it would be very hard to fight bigger music companies in court if they get ever get sued for using unliscenced copyrighted material. I'd just suggest posting it to YouTube as instead it would just put it under the Content ID system and only demonitize your video. Hope this helps, but for more info on how to understand how NG deals with copyright I'd just suggest reading the rules again.
Also some NG creators have gotten away with using copyrighted material in the past which leads to confusion with newer creators, but just because someone was able to get away with it in the past doesn't mean you can get away with it now.
SLUSHIE-SWEETHEART
I have no idea, I've been wondering the same thing. Maybe you should ask in the animation forum as a lot more experienced newgrounders check it often to help people with similar questions.
Kind of unrelated, I really like w.i.p of your animation it looks awesome so far! I'm definitely watching it if you end up being able to post it!
Pandebonium
It’s kind of confusing because I’ve seen people use copyrighted music before but I think they might have just been lucky lol
Also thank you! I’m glad you like it :D