Diff between applying COS L1b-H1b & a petition for H1b

Diff between applying COS L1b-H1b & a petition for H1b separately…how does all this work…who n wen can I apply for COS or do I have to wait till April for the h1b forms…I’m not sure abt al dis since m on L2 but I’m inquisitive to kno abt COS n H1b

COS from any visa status to H-1 can be applied only when the person is present in US at the time of H-1 filing. When it comes to processing, it is usually the same except in case of COS, USCIS also ascertains that the person maintained legal status in US (on L-1 or L-2 or F-1 or H-4) before the H-1 petition was filed. Once the petition has been approved, person w/ COS approved doesn’t need to get H-1 visa stamped prior to starting to work.