1. The same change can be made to each of the words below to create new words.

COVE
CRATE
BADGE

2)
I'm a word of eight letters,
You might say I'm barely there;
Behead me and anagram me,
And I'm an herbal flair.

HINT:
1. The change involves the same single letter.

Answers:

1. Adding an R to each word as the final letter creates new words:

COVER/CRATER/BADGER 

2. SPARSELY/PARSLEY