I mod a ROM Hack which doesnt have a cover so I just used the title screen which includes the games logo:
You need to message people outside of speedrun.com, usually Twitter or Discord.
If it's only one run, better ask the mod of the game, he can add it. If there are multiple runs, you can ask here: https://www.speedrun.com/The_Site/thread/g3wb6
Contact the current moderator for that, this is a last resort in case the current mods are inactive.
Maybe your GCN is newer than the one from the mods or just less used?
I guess your talking about subcategories. To do these, just click on "Edit Game" at the left side and scroll down to "Extra variables/subcategories" and press "New Variable".
Now click on "Use as subcategory".
If you click on the name ("World subcats" in my case) you can change the name of it, this is only visisble to you. In your case it would be something like "Platform" or "Device".
Next to it you can select in which categories you should be able to select it.
Below it, click on "New value" to create a value users can choose from, in your case something like "Mobile", "PC" and "Multiplayer".
To add rules, click on "No Rules", if you want to change them, just click on it.
Your pretty new here so I guess I do a quick explanation: In order to be mod you need to contact the current super mods of a game (indicated by a red sword at the left side). However, they usually only accept people that are already active in the community and already did runs of the game. Another possibility is to request a new game you want to run, if it gets accepted your a mod for it: https://www.speedrun.com/requestgame
I would suggest asking either on the games Discord or on the games forum.
Or actually just try to find a video, i'm sure there are some good tutorials out there.
I heard that 1.6 is more accurate than other ones
Just ask them and tell them that you really want to do that.
I enjoy speedrunning because I have fun doing it and reaching certain goals. WR can be one but doesn't need to be one, I wanted to speedrun other games since months but kept coming back to the one game to get that sub 25...
I actually don't mind if a game has a huge community or not, as long as i'm having fun doing it.
If I understand it correctly, why aren't you allowed to record videos?
I would suggest trying it over and over again outside of the minigame island and then try to remember what exactly you need to do.
I would suggest asking in the games Discord: https://discordapp.com/invite/0idPcnNbLePx1fW8
You need a capture card. If possible, use a internal one! Always!
I recommend elgato HD60 Pro since I didn't had many problems with it, there's also Avermedia and Razer if you prefer these.
If you got a PC and not a Laptop: Internal Capture Cards! Always! I personally use Elgato HD60 Pro and never had any problems with it.