if i have one figure whitout stealth in hindering terrain, other figure with outwit can cancel one of his powers?

Yes. We'll use V Batman from Legacy (Stealth plus Outwit) vs V Icons Superman in this case. Supes can be standing in hindering terrain, but Batman could outwit anything on Supes' dial at this point.

Yes. Hindering terrain does not block LoF. And the appropriate term is counter. FYI.

I'm sure someone else will come along and expound on my answer

thanks

I assume this also applies to Perplex and Probablity Control?

It looks like my friends and I have been misplaying "clear line of fire" for our 3 months of involvement in the game. We were somewhat led to believe that hindering terrain obstructs clear line of fire, since the defense is modified in the case of an attack. However, after reading the rules again, I don't see anything stating that hindering terrain makes the line of fire not clear.

Here are the rules references for anyone else interested:

According to the PAC, the outwitter "must have a clear line of fire to the target"

According to the Icons rule book on page 21:
"Before making a ranged combat attack, you must determine if the attacker has a clear line of fire to the target and if the target is within range. Before declaring your character’s action for that turn, you are allowed to check the map to see which targets are valid targets. To determine if there is a clear line of fire, use any straight edge or draw an imaginary line from the center of the attacker’s square to the center of the target’s square. If the imaginary line passes through a square that contains a character other than the attacker or the target, or if the line of fire crosses blocking terrain, the line of fire is blocked and you cannot make the attack. A line of fire that passes between two adjacent characters, even on an exact diagonal, is blocked. A character can draw a line of fire to itself or to the square it occupies. Soaring characters block line of fire only if the line is being drawn to or from another soaring character. Grounded characters block line of fire only to other grounded characters."

It does. As clixer11 has said, "Hindering terrain does not block LoF."

As you noted, hindering terrain does not block LOF. It does provide a bonus to DV when making a ranged attack, but that is not the same as blocking LOF; if it was, you couldn't make the ranged attack at all.