You can only activate “Freed the Brave Wanderer”’s effect during your Main Phase 1 or 2.
“Freed the Brave Wanderer”’s effect targets 1 monster.
If your opponent chains “Rush Recklessly” to “Freed the Brave Wanderer”’s effect to increase “Freed the Brave Wanderer”’s ATK by 700 points, and the ATK of the target monster is now lower than “Freed the Brave Wanderer”’s ATK when its effect resolves, the target monster is not destroyed.
If your opponent chains “Ring of Destruction” to “Freed the Brave Wanderer”’s effect and destroys it, “Freed the Brave Wanderer”’s effect still resolves.
If you activate and resolve “Freed the Brave Wanderer”’s effect, then remove him from play and return him from play, or flip him face-down then face-up again, you can use his effect again that turn.