Is the command at Gen 2:16-17—not to eat of the tree—the first in the Bible?

It is the first command given to a named, individual man. God created in Gen 1 through words of command, and arguably, “Be fruitful, and multiply” at Gen 1:28 was a command, although it might also, or instead, be a blessing, and anyway it was given to animals as well as the whole race of man. In any event, this is the first instance in which a particular man is given a command that he might rebel against.