Secrets of Sonic 2

It has been awhile since I have played Sonic 2.
It is a frustratingly difficult game.
I kept dying in the flying fortress zone and ran out of lives eventually.

I'm not sure when, but they redid Sonic 2 like they did with Sonic 1. (YAY!!!)
This time, Knuckles is playable from the start. (double yay!)

I was curious as to what the achievements were and noticed a Hidden Palace Zone mixed in there.
I've never heard of it. Anyway, I found out that it was accessible from here (below), in the Mystic Caves Zone 2. Annoyingly, this (I suspect) used to be the pit that would trap you as you could not get out and you could not die. You could only stay in it until you timed out if you fell into it.

Anyway, you can drop into it this time and not just rot to death.

This is the Hidden Palace Zone.

And this looks like a prototype Master Emerald.
(It's a rock that breaks and has a spring in it.)

Eggman with a Trombone!!! I took awhile to figure out how to beat him.
I shall not spoil it here.

And cleared... Goes straight into the Oil Ocean Zone.

And there is a Stage Select cheat too!
Go into the no saved mode, tap the S, E, G, A in the opening screen (you should hear a ring sound) and keep 2 fingers on the screen. Then, the title would come out and you'll go to the stage select. Hidden Palace is there but you can't access it (maybe you would have to find it first).

Also, if you need to find out where you can get the Save Posts in Emerald Hill, you can use the maps found here. A special stage guide can be found here. The special stage is so difficult. You can retry but you'll lose a life while you're at it. You might want to stock up on life to get all the emeralds by Emerald Hill Zone.
 I hope there is Super Tails and (Hyper?) Knuckles. I'll post some pictures soon. =)