Okay, so I can give you a tip.
You want the Wind Laser in the last stage, and the Morning Star.
Wind Laser fires using the BOMB button, not the fire button. This is important.
When you start fighting the core, use the wind laser, exclusively. After a while, you'll get scanned. Once clones start to appear, they'll imitate you. STOP FIRING IMMEDIATELY or you will GET DEAD. Switch to the Morning Star.
Morning Star fires with the regular laser button.
The boss can't imitate it because it didn't scan it. The clones are limited to a shitty pea shooter, and as long as you don't push the bomb button they don't have that either. Your morning star lets you hang out close to the core's weakspot and damage it repeatedly without being in the direct line of fire. It also acts as a shield against the clones, destroying any that get close.
HELL YEAH.
As for the escape tunnel part, I just hope you have amazing eyes, because tracking enemy shots in that mess is a nightmare.