Getting NOC 3 years after resignation - resigned from X on personal reasons by hiding my new offer

While I'm working in private company, I applied for many government jobs and given interviews.
I got selected and joined in autonomous body, say X. At the time of joining they asked to submit the declaration of withdrawing any previously applied jobs.
After 3 months, I also selected for a PSU, say Y, for which I gave interview very before joining the current job i.e., job X
As I want to join PSU, I resigned from X on personal reasons by hiding my new offer.
As of now, I'm working in job Y for 3 years without submitting the NOC. Can I get NOC from X now?

To get NOC after three years of leaving service is impractical and many questions could be asked. You can ask for a copy of the relieving order or of acceptance of resignation. But, is it not better to allow the sleeping dogs to lie....