1. Create cold migration plan with pvcNameTemplate:
{{if eq .DiskIndex .RootDiskIndex}}C{{else if eq .DiskIndex 1}}E{{else if eq .DiskIndex 2}}F{{else if eq .DiskIndex 3}}G{{else}}data{{end}}-{{.DiskIndex}}

Plan failed in Initialization phase, as it doesn't following the DV name rule
-----------------------------------------------------
DataVolume.cdi.kubevirt.io "C-07jwmc" is invalid: [metadata.generateName: Invalid value: "C-0": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')

2. Create warm migration plan with networkNameTemplate with dot
{{if eq .NetworkType "pod"}}pod{{else}}multus-{{.NetworkNamespace}}.{{.NetworkName}}_{{.NetworkIndex}}{{end}}

Plan failed in VirtualMachineCreation phase, as it doesn't follow the interface name rule
-----------------------------------------------------
admission webhook "virtualmachine-validator.kubevirt.io" denied the request: Network interface name can only contain alphabetical characters, numbers, dashes (-) or underscores (_), Network interface name can only contain alphabetical characters, numbers, dashes (-) or underscores (_), must not contain dots, must not contain dots, must not contain dots, must not contain dots

3. Create warm migration plan with volumeNameTemplate with dot '.'/underscores '_', plan failed in VirtualMachineCreation phase
{{.PVCName}}.{{.VolumeIndex}} or {{.PVCName}}_{{.VolumeIndex}} -----------------------------------------------------------------
admission webhook "virtualmachine-validator.kubevirt.io" denied the request: must not contain dots, must not contain dots, must not contain dots, must not contain dots
-----------------------------------------------------------------
admission webhook "virtualmachine-validator.kubevirt.io" denied the request: a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name', or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')

MTV 2.8.0-29 (IIB: 937321) with CNV 4.18.1

Always

pvcNameTemplate:
{{if eq .DiskIndex .RootDiskIndex}}C{{else if eq .DiskIndex 1}}E{{else if eq .DiskIndex 2}}F{{else if eq .DiskIndex 3}}G{{else}}data{{end}}-{{.DiskIndex}}

networkNameTemplate:
{{if eq .NetworkType "pod"}}pod{{else}}multus-{{.NetworkNamespace}}-{{.NetworkName}}-{{.NetworkIndex}}{{end}}

volumeNameTemplate:
{{.PVCName}}-{{.VolumeIndex}}

In step2,4.5: Migration plan failed with error

In step2,4,5: validate the pvcNameTemplate/networkNameTemplate/volumeNameTemplate to follow the DV/interface name rules, and migration plan succeeded