You cannot file for an extension of L1 visa, your employer can. You should have started by talking to the employer's attorney. There is a good chance you could have avoided the need for this question.
Yes, I-94 can be renewed by the employer or their attorney.
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Yes, you can extend it .. by mail to a USCIS dropbox .. not at a local office.
Talk to the company's immigration attorney, not a non-attorney in HR.
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I-94 determines your lawful presence. Your employer will seek extension if they wish you to continue to work on L-1.
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