Central govt rule for promotion/increment

What is  Minimum duration (years )for increment in central government .

One years of qualifying and paid service

how many times one can can get promotion in a year in central government.

as long as promotions are available and he is qualified and suitable

based on no facts described by you no better advise can be given.

please come with facts of the case.

Sir ,The details are mention bellow- 

organization - ESIC

Year of joining in state govt is 2004 (grade pay - 4200)

Date of deputation and willingness in central Govt April 2008 (grade pay-4200 and only deputation allowance)

Date of absorption of state employee to central govt July 2011 (grade pay -4600)

Direct recruited in central 2009 (grade pay-4600) Promotion of both on dec 2013 

1)Why there is pay scale difference between between direct employee and absorb employee if both are on same post .As direct employee drawing more basic pay than absorb employee (difference is two basic)

2)State employee total service is 1o years from 2004 to till date .Can central will consider the state service years while promotion.

3)Is there any way to match the difference ? if yes how to process?

thanks in advance 

It will be difficult to give proper answer without knowing the proper details.

too sketchy details