how do i get other weapons? like the sentry gun and other super weapons?
and is there still a concrete donkey?

Yes there is still a concrete donkey. You can't get them directly by editing your schemes, but you can finish the game to unlock Full Wormage, and you'll have all weapons. (but they are infinite...:( )

And about hidden weapons:
<Worms 4 Directory>\data\Hud\Weapons\pipegun.tga
<Worms 4 Directory>\data\Hud\Weapons\redbull.tga

Is it possible to get these weapons? :D

i finished the game 100%, but there is no full wormage?
i bought all shop items, did all missions, whats left to do?

i finished the game 100%, but there is no full wormage?
i bought all shop items, did all missions, whats left to do?
In W4, the full wormage is named 'the kitchen sink'