Behavior

SO my dog just turned 8months and since I think he has been about 7.5months, he has been really different then he was before, he shows different kinds of attitude not such as biting but creating different difficulties such as peeing around whereas he even used to cry to go out on a walk if he wanted to go... another small example are the tricks that he learned, not too much of a problem but he learned a lot of tricks and one is the eat on command, he literally used to stare me until i said the word eat, now when i haven't even put the food in the bowl he starts to bark on me and then of course doesn't even wait for the command.........Is this all because of age as shihtzus turn into literal dinosaurs after 6months or what? any advice/help......