Is my I-94 still valid till 24-OCT-2019 even if my Employer A revoked my petition?
You are ‘out of status’ NOW as your H1B transfer has been denied and old employer A has already withdrawn your H1B.
Even though your i94 from employer shows as valid till oct 2019 on the face, but you can’t maintain H1B status due to no valid H1B petition.
You should immediately leave USA to avoid any issues later.
Am I eligible for 60 day grace period even with or without Employer A petition revocation?
No, you are NOT eligible for H1B 60 day grace period.
File H1B petition now - new or extesion
Same employer A or B can file your H1B extension now.
But, it has to be done while you are outside US or if you want to stay in USA, you must have some visa to stay on.