140 approved and opted for CP --now In India - PD approaching fast - please help

[beatlemaniac]

Have US masters - then got H1 - employer applied for GC / EB3 in 2009 while I was in the US on their H1 but there was a qn on the PERM and it was denied - I worked in the US until h1 expired and returned to India in time -- lawyers appealed / explained twice between 2009-12 and years later the decision was reversed and PERM approved in 2016 - by pure luck I was consulting (working from home in India) with this employer when the reversal happened and the approval came thru so they filed for 140 within 6 months and it was approved (Feb 2017) with the CP option - with original PD May 2009 - As the PD is nearing - I no longer work for this employer and have a couple of employers who are interested in transferring - they say GC is for future employment - so what if a new employer offers me a job with equal or higher pay - in my case, I can easily prove that its a similar job and profession and duties (I'm into HR) - and the employer is big enough to not worry abt paying me.

Can I change employers now when I go for CP -

if that not possible - worst case, I need to ask my old employer to give me an offer letter ? - (read somewhere that the offer letter is a must and must be notarised and be less than a month old ?)

Can I take that offer letter and get visa approved and then change employers after I land in the US (assuming they give me the visa of course) ?

If I can't change employers immediately after landing - how long do I need to work for the said employer before I can change jobs

Thanks very much