Exit right, and head up the elevator to SRX. Samus will reflect on the real Adam on the way up.
Sector 1 (SRX)
Go through the hatch at the top. Space Jump to the top of the pillar, then charge up a Diffusion Missile and shoot it at the wall. The Rippers below will be frozen, and an Energy Tank will be revealed in the wall. Pull into the tunnel (or stand on the Ripper if it's close enough to the hole) and grab the Tank. Fall down below the Rippers, kill the Gerutas (one releases a red X), and make your way up to the door above, freezing Rippers as necessary. Exit to the next room.
The green stuff will hurt you, so stay out of it. Hurry to the right, running away from the Amoebas that try to attack. Exit right.
Shoot the floor a little to the right of the center to break through. Fall below and head left to a trapped Gravitt. Use two Power Bombs to kill it, moving away from where the Bomb went off to let the free-floating X become a Geruta. Kill the Geruta, and let the X become a Golden Space Pirate. Only its back is vulnerable, so you must approach it to make it jump over you, then quickly turn around and shoot a Missile at its back. Three Missiles will kill it. Collect all the free-floating X it leaves behind, possibly including a red one, and head through the hatch to the right that is now open. Collect the Power Bomb Tank, then return to the last room and Space Jump up through the hole in the ceiling to go back above.
Exit right to a Save Room, then return to the shaft and Space Jump to a ladder above. Climb up to become a ball in the narrow space. Get onto the ledge above, and bomb the right wall to reveal another ladder. Climb to the top, avoid the attacks of the Space Pirate if you can (let it jump over you) and just go through the door.
In the next room, use Power Bombs to kill the creatures in the floor below (move out of the way so the X don't touch you). The wall to the left will be destroyed, and the X become a Golden Space Pirate. Kill it as before, and the X will become another one. Kill it, and then you can go through the door to the left.
Go and save in the Save Room above, because a battle is coming up. Fall below and exit left. Freeze the Rippers and make your way to the Living Door to the left. Kill it, grab the red X, and go through the door. You'll fall below to find the apparently fossilized (or something) remains of Ridley. Approach it and its eye will glow, then stand back and it will scream and transform into an even bigger and far more menacing version of itself.
You may recognize the background music from Super Metroid. Use charged shots against Ridley-X (Missiles will work, but a charged shot will keep damaging Ridley-X as it passes through it). Keep holding L to aim up at the monster, and just keep charging and shooting your beam at it. Try to avoid the fireballs it spews as best you can. If Ridley-X grabs you, shoot up at it with Missiles until it lets go.
Eventually Ridley-X will start using its tail against you. It will lash out at you with it, and will also move back and forth stabbing down at you with it, like in Super Metroid. Keep fighting it until it screams a lot and becomes a Core-X.
Six Missiles will destroy the Core-X's membrane. Grab the Core-X to regain your Screw Attack ability. Now, when you Space Jump, you will glow with an energy that can kill pretty much all enemies instantly, and break through Screw Attack blocks, Bomb Blocks, and some other breakable blocks (but not Boost Blocks or Pit Blocks).