Tier 2 General - Change of Employer

[Sudhakar31]

Hi Team,

Thanks for all your help in the past on my queries. This is one of the great forum for expats like me to get excellent clarification on UKBA Process.

I'm on Tier 2 General Visa from August 2012 which expires by 2015. But I've a job offer who is willing to Sponsor new Tier2 Visa. I understand the process is getting new COS, documents from new employer, then apply Tier2 Fresh application. So as per good practice, it is better to inform my current employer only after my New visa with new employer is approved & visa stamped. My questions are:

1. Is it illegal to work on new visa with current employer? If that's the case, what will happen to notice period?
2. Is there any impact on ILR application in the future (which is 2017)
3. What will be the duration of the new Visa? Will be it 3 years or less?
4. What is the duration of visa process?

Thanks for your help.
Sudhakar S