Ok! as I said, the extra two SAS cables are optional, so if it is a great expense, don't worry about it.
The ACP is used for monitoring and some automated management (ACP = Alternate Control Path), but there is no way to login to the shelves manually.
First configuration must be over serial "IOIOI" - 9600, 8N1 - once ONTAP is running, you can run "sp setup" to set an Out of Band IP address and login to the service processor IP, or then use System Manager to connect via GUI. For more details, please let me know what version and mode (7 or cluster) of ONTAP you are running