Jupiter Screen 8-9-10-11

This screen requires very tight movement.

First 3 enemies

Land on the top platform, and use a Pluto Break Dash through the Joe. Completely ignore the Hammer enemy on the bottom.

Your goal from here is to either use the Pluto iframes to get through the magnet enemy, or just destroy it.

Optimal Strat (Difficult)

Move quickly enough to let Pluto iframes absorb the magnet enemy's shot. Proceed quickly before the Magnet enemy returns.

Old Strat (Slower)

After break Dashing through the Joe, switch to Neptune. Hold up and Right on the shot (?) to launch Salt Water at the magnet enemy to destroy it.

Checkpoint Joe

The last enemy on this screen is also the last enemy before the checkpoint. Falling in the pit here sends you all the way back.

Many strats here boil down to damage boosting on the right side of the Joe, so you don't get bonked back into the pit. 

Alternatively, this Joe may be worth switching to Buster and shooting the Joe. Keep in mind its shot will hit you if you "just stand there".

Screen 9

Checkpoint screen.

Screen 10

There is another bouncy ball enemy and a ladder at the top right.

You can use Neptune or the Mega Buster on the ball enemy, or Pluto to bypass it. 

Screen 11

There's a Joe guarding some items trapped behind blocks. Climb the ladder and move on. You can do the "drop off the ladder to jump up faster" technique here if desired.

There is no reason not to collect the items other than the time it takes to collect them.