My puppy is 9 weeks, and I got him when he was 7 weeks. So he's still super young. He is also my very first dog that I'm training. When I tell him no, he seems to understand and stop what he's doing that's naughty. But other times he sasses me, as in he'll bark at me. He does that when he's biting/chewing on my hands, feet, or ankles. But other times he just straight out bites me way harder than what he was doing. He'll even nip/bite me on other places than my hands, feet, or ankles. He's lunged at my face a few times as well. So I'm not sure if that's just him playing or not because he does seem to understand the word no. When he does do that he chases me sometimes when I try to go get a toy if I'm not by one. My mom told me I should squirt him with some water. Which does seem to get him to stop but he starts back up a lil after or once I turn my back.