To lower and to raise are verbs. ex: The merchant lowered the price for the holiday and then raised the price afterwards. Lower and upper are adjectives. ex: The lower floor of the home was full of expensive furniture, but the upper floor was completely empty. Lower and higher are adjectives. ex: This is a lower price than at the other store. This is a higher price than at the other store. Lower and higher are adverbs. ex: The plane went lower so the passengers could see the whale. The plane went higher to go over the mountain range.

No, 'upper' is never used as a verb. You need to use verbs like 'lift', 'raise', 'elevate', 'higher', etc "Lower your arms". "Now raise/lift them". "The lower we go in the cave, the darker it gets." "The higher we go, the brighter it gets".

No because upper is an adjective when describing its relationship to something else or someone else or somewhere else. Upper is a noun when describing something like your upper body etc, your torso the part above your waist. "the upper mineshaft" is a noun when distinguishing between two parts of a mine shaft the lower or the upper parts of a mineshaft, or between two mine shafts one named/called/known as/designated as "the upper" and the other as "the lower"

The simple answer is no, it is never used as a verb.

You have a point, Angela. That's the beauty of English, I think.