Courageous has three syllables and is an adjective, out in this the second syllable is stressed cu-RA-js.
Yes adult has 2 pronunciations, one of them the first syllable is stressed which makes the first sound a pure vowel and in the second one, second syllable is stressed making the first sound as shwa (inverted e).
As a thumb rule the stressed syllable will always have a pure vowel sound and destressed syllable will have a short shwa sound.
Controversy also has 2 pronunciations differing on the basis of which syllable is stressed. Both the pronunciations are accepted.