H1 COS Approved while L1B ext pending,Missed to Apply L2 to H4 COS,

Currently on L1B through Employer A , for L1B and L2 extension before Expiry got RFE, status of L2 still shows inprogress.

Employer B applied for H1B COS much before my L1B Expirey and
Mean while H1B from employer B got approved, but he missed to apply L2 to H4 COS for spouse.

Now we are plannign to apply L2 to H4 COS for dependents.I am Planning to join H1 employer in November.

Questions :
1)Can I join H1B even my L1B extension is still pending?
2)what about dependents status ,in status? how soon should I convert L2 TO H4
3)since my H1 is approved and H1 Employer missed to apply L2 , what are chances of getting L2 to H4 COS with out leaving country.
4) Employer B is telling that he will apply L2 to H4 COS this week, will that be okay ? does it create any problems. Please let me know.

  1. You are expected to join H-1 employer from the COS effective date. This holds true irrespective of whether L-1 extension has been filed or not

2, 3, 4. Your attorney should have been smart enough to include their COS along w/ your H-1 petition. When is your COS effective date?