generally I would always listen to the floor guy over the contractor when questions arise about the floor

my answer would be depends on the brand/type of finish being used.
normally two is fine over stain, three doesn't hurt.
for example, on my stain jobs ill do two coats of finish unless I waterpop in which case I do three.

I do not know if it would be noticeable to do 3 coats over the stain in the laundry and kitchen and 2 in all the other rooms that run into the kitchen. I will have to ask that question. Not sure what "waterpop" is. Thanks for your advice.

waterpoping is just a technique used to stain some species of wood and darker color stains. just ask your floor guy if he is or not.

If theres nice cut off points to each potential rooms you don't want 3 coats. then that's totally possible and if done properly you wont notice...especially after a few months of your normal wear and tear. but it all depends on what your floor guy suggests. That's Key!