No.
An adjective that precedes the noun it modifies is in the attributive position. In this position, the adjective directly describes the noun and typically comes before it in a sentence, such as in "the red apple." This contrasts with the predicative position, where the adjective follows a linking verb, like in "the apple is red."
The Predicate position.
attributive position
Yes, "nineteenth" is an adjective that describes the position or quantity of something in the series of nineteen.
No, neither word is being used as an adverb. Position is a noun and upright is an adjective describing the position desired.
Yes, "elected" is an adjective. It describes something or someone that has been chosen for a position through a voting process.
both
That is the correct spelling of the adjective "transposed" (switched in position).
The word twelfth is an adjective. It can also be a noun.
On can be an adverb a preposition or an adjective. adverb - Turn the lights on. adjective - The switch is in the on position. preposition - I'll see you on Sunday.
Sometimes it is considered one, but it is a preposition or adverb. As an adjective it means 'in a crossed position' (e.g. seated with his arms across). But this would more properly be the adjective "crossed."
Position is a preposition