All information relates to the specific ROM: “Metroid II - Return of Samus (UE) [!].gb”, it is 256 KB in size (262,144 bytes).
A list of guides created by the community, from manuals on the tools themselves to advanced guides relating to ASM, its all here.
Manuals of the workings of all the editors and utilities available to you, detailing all their functions.
These guides cover all the basic things around editing Metroid II, as well as serving as a good starting point for learning how to get into Metroid II hacking!
These guides assume you have a good basic knowledge about editing Metroid II already, you should probably be comfortable with using (editor) by now and be moving onto using tools like a hex editor.
These guides could be pretty complex, you should probably be comfortable with assembly by now.
This segment is reserved for technical information on Metroid II, to be used as reference material for hackers, or for the curious wanting to know what makes Samus tick, or possibly you are interested in making a fan game and want to know how Metroid II does things!