Betray, Destroy, and Obey do not need to be changed to add the suffix -ed, because the "y" at the end of each word is preceded by a vowel (so they would be spelled "betrayed," "destroyed," and "obeyed").
But hurry is different; it has to be spelled "hurried" because the "y" at the end of "hurry" is preceded by a consonant.
the exact definition of natural vegetation is a cover of plants that can grow alone with little to no human interference, so i believe this fits your description best!