title: Update viewpager fragment specific position and get back to previous while backpress
body: <p>I have a view-pager with two fragment in it . based on my logic i want to replace the fragment on a specific position with another fragment but when user back-press i want to go back to previous fragment i replaced with it </p>
  
  <p><strong>for clearance 
  i have 4 fragment A, B, C, D   initially i added A and B to view-pager, then i replaced B with c in view-pager , So that i want  is to go back to fragment B (replaced by C) from C (current) while pressing back button instead of going back to another activity</strong> </p>