Current Linux kernels operate correctly with older versions of Hyper-V back to Windows Server 2012 Hyper-V. Support for running on the original Hyper-V release in Windows Server 2008/2008 R2 has been removed.
A Linux guest on Hyper-V outputs in dmesg the version of Hyper-V it is running on. This version is in the form of a Windows build number and is for display purposes only. Linux code does not test this version number at runtime to determine available features and functionality. Hyper-V indicates feature/function availability via flags in synthetic MSRs that Hyper-V provides to the guest, and the guest code tests these flags.
VMBus has its own protocol version that is negotiated during the initial VMBus connection from the guest to Hyper-V. This version number is also output to dmesg during boot. This version number is checked in a few places in the code to determine if specific functionality is present.
Furthermore, each synthetic device on VMBus also has a protocol version that is separate from the VMBus protocol version. Device drivers for these synthetic devices typically negotiate the device protocol version, and may test that protocol version to determine if specific device functionality is present.