GC processing requirements for an employee on L1B visa

Could you please help me in understanding the GC processing requirements for an employee on L1B visa.

  1. In order for an employee who is on L1B visa to apply for GC under EB2 category, is there a pre-requisite that he/she should be on valid visa during the entire length of GC process or GC can be initiated even if he/she is on valid 1-94 ?
  2. For employee who get their I-140 approved on H1B visa under EB2 category will no longer need to worry on the length of stay ( I mean they can stay even after 6 years). 6 years term constraint will not be there. Is it the same in case of associates on L1B. If they get their I-140 approved under EB2 category before 5 years of their stay, are they legally allowed to stay or should they need to leave US for one year ? will they have 5 year term constraint even after getting I-140 approved ?