To which layer of the OSI model would the ACI concepts of policy, AEP and physical and VMM domains?

An override policy at AEP can be used to specify a different physical interface policy for a VMM domain. This policy is useful in scenarios where a hypervisor is connected to the leaf switch through an intermediate Layer 2 node, and a different policy is desired at the leaf switch and hypervisor physical ports. For example, you can configure LACP between a leaf switch and a Layer 2 node. At the same time, you can disable LACP between the hypervisor and the Layer 2 switch by disabling LACP under the AEP override policy.
The layer 2 is Data link layer
Reference: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/1-x/aci-fundamentals/b_ACI-Fundamentals/b_ACI_Fundamentals_BigBook_chapter_0111.html