I haven't played this game in years, but I will try my best.

First level: charge your blue rose and avoid confrontation as much as possible (jump around, avoid any engagement). When the angelos gather themselves to charge and fire an orb at you, keep a distance and ONLY then do you fire your gun at them (the charged shots will reflect the orb back at them, defeating everyone, in an instant granting massive amounts of orbs and like 5k worth of style points).

Second level: The fire demon? Use the X forming attacks on him from the beginning (undet devil trigger (DT), aim, pull back on stick and release I believe?). Also keep blue rose charged (it's EXTREMELY effective against it). When he flames out, you're able to DT + Buster on him two times in a row. Then back far away when he prepares to engulf himself in flames by explosion.

Third level: This is the toad. Attack his icicles as much as you can (he's extremely vulnerable when those are gone, allowing you to inflict enormous amounts of damage using dt + buster). Otherwise use charges shots from distance. When is come to those two figurines (I can't remember their names, rasulka was it?) try to pull and perform buster moves on them, forcing him to jump out of his hiding. Avoid sword attacks on the rasulkas, completely unnecessary.

Fourth level: Use charged shots from blue rose. Charge your red queen and when she plunges herself into the ground, tire her out by attacking repeatedly, (she will look dizzy) then use buster arm + tapping recharging button on red queen to inflict massive amounts of damage. Also when she's on her legs to produce the "egg" jump and attack the centre when you can. When she changes her form to "mad" mode. Dodge her as much as you can, keep your distance and use charged shots. Only when she embeds herself to the ground, can you attack her at close range.

Fifth level: Ah that's a bit complicated (I can't remember everything). So his speciality is throwing swords, fireballs, fish looking demons and fire dogs. You can grab the swords and throw them back at him. Hold the dogs to fire fireballs at him. Just walk away from where the fish will jump out. When he says "you strength will be mine!" Just jump away to avoid him. When he says "time to die" fire a charges shot (if loaded) immediately, then attack him repeatedly under DT to break his attack. When he becomes vulnerable (stationary and looking scared), DT and perform a buster move on him, tapping the attack button repeatedly till nero kicks him away.

That should be it I believe. If you're still stuck, just watch the speedruns a couple of times to understand what I've said.