Yes, you can there is no such bar.

You will not be loosing this job as you got earlier job without using quota.

Incase you are loosing this job you cannot claim earlier job

Ex-serviceman can’t avail job quota benefit twice.

So he has no case and locus standi to challege your appointment. 

There is nothing wrong in your case as you have not availed state government quota for the ex servicemen you have the opportunity to avail this facility however your previous employment which was not based on the quota for ex servicemen maybe resigned and even in case any case in this  regard is file may be liable to be dismissed

If case goes against you file appeal against impugned order 

you di snot avail Ex service men quota for your earlier job hence you should not be denied benefit 

What are prayers of ex-serviceman  in his case who has challenged your appointment?

It is an important part and factor to know whether you would fail or succeed in the matter filed by him against you.

You cannot claim earlier job until or unless you were expelled from that job on the wrongful ground or which will be unlawful in terms of rules and regulations of the government or in the contravention of fundamental rights.

-  As per the rule 2 of Ex-servicemen (Re-employment in Central civil services and posts) rules 2012 doesn’t permit second time use of ex-serviceman status for getting a government job.

- Hence, if a person gets a government job under the ex-serviceman quota, he/she can’t avail the benefit of reservation for re-employment.
- Since, you got the employment under state government without availing the quota , and further you got the job in state civil service after availing quota , then this serve is under the rule , and cannot be challenge on any ground , as you have availed one time benefit. 

- Hence , that case filed by that employee is against the rule , and legally not sustainable .

- However, if this case goes against you, then you cannot avail the second job on quota basis , but can claim the first job legally. 

1. If you have abruptly resigned the earlier job, you cannot claim the previous job for any reason, because this is not a technical resignation so that you can operate lien period.

2. You can file a writ petition or appeal before appellate court if the decision is going against you.

You need to give technical resignation I'm such circumstances then join so that you can get the earlier post if not continued in the new one

ex-servicemen from joining civil employment if they have already availed the benefit once, will not be eligible to get for the second time. 

Yes but you should go for appeal before Supreme court in which you seek reinstating to this job or previous job. 

1. As per the information mentioned in the present query, makes it clear that the earlier job that you had got was not on the quota.
2. I would like to apprise you that the thing which you want if you happen to lose the case, is not at all practical to be think about for happening.
3. In fact, your case is very strong in your favour aspect, so would advice you to not to think about much about it and just contest the case. As it is so clear that you didn’t take up the opportunity of availing quota in that job so now you can’t be penalised for the same.

If your papers are in order and you haven't committed any fraud then your case has merits and hence there can be no adverse judgment against you.

The job you left or lost cannot be now taken.