Admiral David Glasgow Farragut was the first American Naval Officer to obtain and hold all 3 Admiral ranks.

Nikki Snelson's birth name is Nicole Ruth Snelson.

Depending on the particular rank of Rear Admiral (Rear Admiral or Rear Admiral(lower half) the abbreviations are:

Rear Admiral - RADM (O-8)

Rear Admiral(lower half) - RDML (O-7)

RDML is similar to a Lieutenant (Junior Grade) in that it is the lowest and most junior of the Admiral ranks.

To address a Rear Admiral in letter form it's 'Admiral.'

Admiral