Hi,   As of now FCF is must, because ACI fabric do support FC/FCoE NPV mode only. To support your requirement, connecting Storage directly to the Leaf without the FCF, Switch mode support is required on ACI Leaf. Currently ACI Fabric don't support FC...

Yes ACI 4.0.x is recommended for Production. 

Hi,   From ACI release 4.0 there is support for Native FC (32G) on N9K-C93180YC-FX switch.   More details can be found in below link.   https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/4-x/L2-configuration/Cisco-APIC-Layer-2-Conf...