I am selected for govt job but not resigned from old job. Advise

I had joined the PSU owned by state government in 2005.During probation period i.e. in 2006 I have applied for without pay Educational leave(It was not sanctioned by office without worrying about it , i went for PG education).Even after completion of education , i didn't joined it nor I resigned.I don't remember exactly but in 2010 / 2011 I received a letter mentioning that "You left the office with sanctioned leave , you are supposed to join the office within 8 days from receipt of this letter otherwise you will have to face action based on disobedience". Since then no oral/written communication from office.Recently I have selected by State Public Commision as Gazetted officer Class "A".Before joining state government wants me to fill the attestation form wherein I am supposed to give the details of jobs i have done in past.I fear that if they equire @ my record at PSU (Where I was working in year 2006) and if they find me not reliable ,my new joining will not be accepted.As this form