I am having valid L1 visa and have been in US for 6 months with employer A. During my stay, I have got my current project over and needed to return back to India. During that period, I got a H1B sponsor(employer B) and have sent him necessary documents for H1 petition and returned back to India. Now, this employer B is not proactive and I have to be on back of him for my updates regarding H1 visa and everything. Recently, he has said he applied my H1 visa but I didn't get any receipt number from him.
My question is, Can I be with my current employer A with my L1 visa now and can go back to US with this L1 visa (whether or not my H1 is applied by employer B)? Please reply to my question as I am not able to make my mind on this? Thanks in advance.

Yes. Your L-1 visa is valid and you are currently employed by the company.

The H-1B petition has been filed and you are outside of the US, then they can only file for the H approval, not a change of status. The USCIS has no jurisdiction over you if you are not in the US, only over the H petitioner. You are also not yet working for the company, so there is no H-1B in effect until you get the H-1B visa in your passport and are admitted to the US.

Bottom line is that you are not an employee of the new company and you are not an H-1B. You are an employee of your current company and have an L-1 visa.

Thank you for your input. I have a follow-up query for your answer:
Can you let me know what is the H1 process? My understanding is, after filing H1 petition, new employer has to file "Change of status" which can be filed only when I am in US.

That is incorrect.

There are 2 ways, depending on whether you are in the US or outside the US.

As you are outside the US, the petitioner (employer) files the H-1B petition (I-129, etc.) and the USCIS issues an approval (I-797, Notice of Action). You then take that approval notice and apply for the visa at your home consulate, if issued, you use that for admission to the US. You will be given an I-94 annotated H-1B and you are then authorized for employment with that company.

If you are inside the US, then the company files the H-1B petition (same as above), but request the change of status, from your current immigration status (L-1?). If approved, then the I-797 with the newly annotated I-94 serves as evidence your employment authorized status.

I hope that this is responsive to your inquiry. You should find an immigration attorney to advise you further. Good luck.