L1B extension or L1A conversion to fall under EB1?

[sujay_hsk]

Hi i have Blanket L1B and currently in India(my home country) and working as Manager from past 1.5 yrs . Now, i have got a transfer offer to my US head office as a Manager. My L1B is expiring in Aug 2016, but i still have 2 more years under L1B, as earlier only 3 years has been granted. Also i have all hire/fire, appraisal and leave approval authority both in India and US. Hence, i believe i make a strong case for L1A. So below are my queries:
• Should i apply for L1B to L1A conversion before moving to US?
• If my L1A application is denied, will my existing L1B status remain as it is?
• What is the duration it takes for me to know the result of my L1A petition, if I do it from India? As i have to be in US in next 3 weeks.
• Or is it better to apply for conversion after moving to US? If so, do i need to come to India for Visa interview or for stamping?
• if i move to US with L1B, will my employer be able to apply my GC under EB1C?

Please let me know what would be the best approach so that my GC application falls under EB1C?

Earlier, I have been to US 3 times in 2013 and 2014 but each time i have stayed for just 3-4 months and have returned to my home country India. So no application was filed for my GC, Labor certificate or SSN.

Thanks