spy-guy, you are right with everything you said, however I know from experience if you down shift you car from regular "D" drive into "1" 1st gear it will not go into first if you are above a certain speed and rpm range. I was exiting the expressway moving about 50 mph and due to weather conditions had my shifter in the "D" position not "OD" and when I exit the expressway I usually down shift out of "OD"overdrive to "D", last winter I shifted into "1" 1st gear and just as I did it I thought to my self "oh s***" I am going to f---up my trans, then just before I was going to quick shift back into "D" I realized the rpm's did not start to scream like I anticipated, it instead only went up to about 4000 and slowed the car nicely and then again when the transmission knew it was safe to down s*** again, it did so very smoothly to my surprise.
Now if you are at a stand still the transmission will not shift higher then the selected gear., but it will down shift safely