Supported offline handoff boundary for a macOS VM disk image and auxiliary storage

We need a supported checkpoint after macOS installation before an independent process verifies and later boots the VM. We distinguish installer success, actual VM stopped state, application queue drain, reference release, and file synchronization.

1. After installation completes without error and the same VM is stopped, can Virtualization still submit writes to the disk image or auxiliary storage? What documented barrier ends them?
2. Does releasing all application references and autorelease scopes and draining the VM queue end storage writes by all SDK objects, internal tasks, and services?
3. After the producer process exits and is waited for, can services, transferred handles, or pending framework buffers still modify either file?
4. Is there a supported joint durability/consistency boundary for disk and auxiliary storage beyond the disk image Full guest-flush guarantee?
5. What handoff sequence and platform versions does Apple support for sequential installation, offline verification, and boot processes?

We are asking for the contract, not proposing forced stop, delayed hashing, or an undocumented recovery procedure.