1. Is it possible to copy a brush from one map to another?
Eg. I want to copy a vehicle from a.map to b.rmf.
2. Is it possible to convert .map to .rmf?
3. Is it possible to create a whirlwind?
Maybe using func_push?
4. How do you make the flashbang effect?
Some maps have flashbangs popping out of nowhere at a certain point and blinding you, like one of the NBnoobgames.
1) Yes, you can make it a prefab. Select the whole thing, then go to Tools->Create Prefab.
2) You can load the .map into hammer and then save it as .rmf.
3) Depends on what kind of whirlwind you want. You could make a simple one that raises you and spins you in a "circle" using func_push, yes.
4) My guess is it is done with sprites. Not sure about this one though.
...and that's the bottom line because Mate de Vita said so.
Who controls the past, controls the future. Who controls the present, controls the past.