No, the L-1B visa ties your employment to the U.S. affiliate.
Yes, any person can start a business in the U.S. without regard to immigration status, however, only persons with proper authorization to work in the U.S. can be employed by that business.
The transferring employee may bring a spouse and any unmarried dependent children under the age of 21, upon approval of their L-2 visa application.
Spouses of L-1B workers now automatically have unrestricted work authorization ‘incident to status’ without needing to apply to USCIS for any employment authorization document. Proof of that work authorization will be placed in the spouse’s I-94 when USCIS implements new notations, until that time, spouses should still apply for an employment authorization document (EAD).