Attacks » Altered Creation GX | Trainers » Channeler
Does Channeler negate the effects of Arceus & Dialga & Palkia GX's "Altered Creation GX" attack?
It depends on who is playing the Channeler. If the player who used Altered Creation GX uses Channeler then the effects are removed; the player's Pokemon no longer do +30 damage and the player does not get to take any extra prizes from the effect. However, if the player's opponent plays Channeler, then Altered Creation GX effects are not removed as they reside on the other player (who did not play Channeler).
Source: TPCi Rules Team (2020-01-09)
Trainers » Channeler | Attacks » Clear Vision GX
If my opponent used Latios GX's "Clear Vision GX" attack on me, could I use Channeler to remove that effect?
Yes you could, because Channeler removes effects from both you and your Pokemon.
Source: TPCi Rules Team (2019-08-01), TPCi Rules Team (2019-09-05)
Trainers » Channeler | Attacks » Knockout Reviver
If I used Poipole's "Knockout Reviver" attack, but then on my opponent's next turn they play Channeler, would that allow them to take a prize for KO'ing Poipole?
No, it would not. The effect of Knockout Reviver resides on Poipole, and the opponent's Channeler only clears effects on the opponent or their Pokemon.
Source: TPCi Rules Team (2019-08-22)
Trainers » Channeler | Attacks » Gigaton Shake
If I used Steelix's "Gigaton Shake" on my previous turn, would Channeler allow my Pokemon to attack this turn?
Yes, the effect of Gigaton Shake would be removed, and your Pokemon would be able to attack.
Source: Unified Minds FAQ (2019-07-19), TPCi Rules Team (2019-08-01)