Hdfc bank Salary account for non corporate salary relation Employer how?

1. No idea. 

2. For existing salary account holders who changes job and new employer does not have a corporate salary account relationship then how to continue salary account

Answer is quite simple: Just by doing nothing. 

You don't have to do anything even if you change employer and that company has no relation with HDFC. It will not affect your salary account at all. The only thing that really matters is you should some credit in your account every month be it through ACH, RTGS, NEFT or even UPI. 

I know many who have not received salary in their HDFC account in years, but still there account is not converted to normal savings account. Generally banks have a lot of matters to tackle so, they don't focus on these things much. 

hmm i have one doubt now hmm can we have 2 salary accounts in different banks (like axis 1 salary account and hdfc 1 salary account) by some trick?

I know its not possible because of EPFO credit but still would like to know any sustainable ways available?