Which mountain peak was explored first, Sunanda Devi or Annapurna II? 
Sunanda Devi:  The first ascent to the Sunanda Devi peak in recorded history appears to be in 1939 by Jakub Bujak and Janusz Klarner. Annapurna II:  It was first climbed in 1960 by a British/Indian/Nepalese team led by J. O. M. Roberts via the West Ridge, approached from the north.
Sunanda Devi