No, you may not. Invited guests ARE NOT permitted to bring anyone to neither the ceremony, nor the reception, whom the bride and groom did not personally invite/address an invitation to. All guests will be required to sign-in in the lobby before being allowed to take the elevator up to the ceremony. If a name is not on the list, the person will be asked to leave. No exceptions.
No, you will not be able to enter the ceremony once it has began. The doors will be locked and you will have to wait in the elevator lobby until the ceremony concludes and cocktail hour begins. Thus, please be on-time.