Can I Get an NOC from My Previous Job 3 Years After Resigning Without Disclosure?

While working in a private company, I applied for many government jobs and attended interviews. I got selected and joined an autonomous body, let's call it X. Upon joining, they requested a declaration stating the withdrawal of any previously applied jobs. Three months later, I was also selected for a PSU, let's say Y, for which I had interviewed before joining X.

Wanting to join the PSU, I resigned from X for personal reasons without disclosing my new offer. Currently, I have been working at job Y for three years without submitting the NOC. Is it possible for me to obtain the NOC from X at this point?

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....