I couldn't find much examples from HLD, but assuming that it's just a normal top down game, that means you have to animate an attack in 3 perspectives, from the front, back and the side. If the attack is asymmetric you will have to make a 2 side animations, for example when a sword is in your left hand.
How many frames something has is really not set. That totally depends on how many frames are required and how many the dev actually wants. Since more frames = smoother animation (this doesn't mean more frames is always better).
For your 360 degree rotation you should rotate the sprite of the weapon by code, probably. Maybe look at Enter the Gungeon and Nuclear Throne for how they do that.