Salary components for esic

dear sir if employee gross salary fixxed at the time of appointment above 21000 then is that employeee permanenatly not eleigle for esic ???

and what salary components consider for 21000 threshold  i.e is 21000 basic salary or basic hra and conveyance allowance etc included   ????

if employee totally 27 days absent 3 days present then his salary 4500   in dec18  inprevious month  he is not eleigible for esic   so in dec18 is he eligible fo resic  for reason of his salary below 21000   plz reply me    

i have three doughts