Process of employment transfer

I hope  I could get an answers to my situation.Im currently employed in a government sector and had decided to resigned after my 1 year tenure with the company and they approved my resignation.I found a new employment offer in a private sector.Here are my questions.

1. Can I still be employed by a private company if I dont get an NOC from my current employer,even if I will leave Oman and cancel my current working visa/permit?
2. Can I return to Oman within 2-4 weeks after my cancellation date as Im planning to exit to Dubai and wait there until my new employer starts the process of my employment?
3. When travelling to Dubai as tourist,will immigration ask for proof of return ticket to my home country since I dont have anymore a valid resident  permit in Oman?
4. Is there a way to reactivate my nursing license when I come back to a new employer after my current registration has become inactive due to leaving my current job?Do I need to re-take the prometric exam?