I have to write the prepositional phrase, the word it modifies, and whether the phrase is an adverb or adjective

Question

Mold-maker robots inject red-hot metal into molds.

preposition phrase into molds
modifies metal or inject?
if metal adjective
if inject adverb

Mechanical arms move systematically down an assembly line.

prep phrase is down an assembly line
modifies how they move
adverb?

Answer 1

"Into molds" modifies injects because it tells where.
Adjectives tells which, what kind of, or how many. Adverbs tell where, when, why, how.

Your second answer is right.

Answer 2

how about this one:

Arc welding is another job among the many risky jobs that robots perform.

prep phrase: among the many risky jobs
modifies: arc welding
adjective

Answer 3

I agree with your last answer.