Mine quickly understood about 60 of my words & phrases but strangely NO was never in his vocabulary!
I reasoned that buns might take more notice of a warning of danger,(brain wired to predator avoidance). Saying "careful" in a frightened voice, & imagining the consequences of e.g. a dead bunny if he ate wall paper, worked a treat, but ONLY if he hadn't done it repeatedly & safely before.
As he grew older & more bonded to me, I just had to drop my voice, "Thumper"! & he'd jump in the air & turn his back to temptation. It was so cute.
ETA with inappropriate chewing I'd offer him a bark covered stick/appropriate chew, as soon as he drew back from the wrong thing.