Hello,

If my opponent has multiple (let's say 2) Hunting Spears in his army (on one or several characters), will all my characters without Weapon suffer a -4 or -2 STR penalty? I guess it's -4 but I want to be sure.

About Kinswood Trail, I'm 95% sure but if my opponent has 2 of them and declares a power challenge, he can kneel 2 of my characters with a power icon right?

Thx

Correct.

Every card is considered a separate and individual card, even if it has the same title and another card. And every separate and individual card is resolved separately and individually (surprise...). So each copy is resolved once, which has the practical effect of having the effect applied twice.