In the worms 4 mayhem's folder,in the map section,there are many hidden maps,for example nomoreislands.xam(its like the no more islands map in worms 3d).If u rename this map to a normal map(for example multi_nicetoseigeyou.xan),u can play it without problems.
The question is:this map, can be unlocked in the game?(i complete the 100% of the game)

no, they cannot be unlocked. they are not in the map list. most of them are left over from the development.

yes,i think it is only a map test

It can't be unlocked, but you can do the following:

Get a map file you have unlocked that is in the game (for example HighNoonHiJinx.xan if you've unlocked it)
Rename it to *name here*bu.xan (eg HighNoonHiJinxBU.xan). It doesn't actually matter what you call it, in this case BU stands for backup.
Get the map you want to unlock
rename it to, in this case, HighNoonHiJinx.xan
Go into the game OFFLINE (online will crash) and play the game set to High Noon Hi Jinx map
WOOT!


EDIT: Damn me at my not reading the thread! You've already found how to do that! I might post a link to K^2's map VIEWER (not the editor) so it makes this easier.

EDIT2: Here it is. Instructions: use the arrow keys to change view, use the ESDF keys to move. It's in black-and-white only, but it is quite good to see roughly what a map looks like.

Also, you must press esc to close it; the X doesn't work unless you move the window. I know it's for worms3d, but it works equally well with worms 4. You MUST drag the map to the program, or double click the map, click select program from a list, click browse, and find the map viewer. It doesn't work just double clicking o the program itself.

there are two more things to keep in mind.
1) if the map has .hmp file with the same name associated with it, you must rename both. .hmp contains the height map for the level. it is not visible in k^2's map viewer.
2) the theme for the map is stored in the map list. that means that the map you want to view will be seen with the theme stored for the map that you replaced. if you guess the theme wrong, it will look pants.

there is a potential for editing the map list, so you don't have to worry about that stuff, but to my knowledge, such an editor does not yet exist.

well,ive tried,but once i load the game,whole screen is yellow

try the "realyrace.xan" its wonderfull,i completec it in 80 sec,walking no flying.