Question: I want to change release names like `V.1.0.00` for manual release in Continuous Delivery of Azure DevOps but i can't able to delete or change the naming without this `$(rev:r)`, how can I use a custom name?

Default Name: `Release- $(rev:r)`

Required Name: `V.1.0.0`

Answer: 
In the build Pipeline.

You can customize how your pipeline runs are named/numbered. Ref : <https://learn.microsoft.com/en-us/azure/devops/pipelines/process/run-number?view=azure-devops&tabs=yaml>

In YAML, this property is called name.

Use variables to set your major version, minor version etc and generate the patch version using counter Ref : <https://learn.microsoft.com/en-us/azure/devops/pipelines/process/expressions?view=azure-devops#counter>.

for your case you can set
major : V.1
minor : 0
patch : $[counter(format('{0}.{1}', variables['major'], variables['minor']), 1)]

and set the name like 
name: $(major\_version).$(minor\_version).$(patch\_version)

Release pipeline

Refer to $(Build.BuildNumber) which will ref to the buildpipeline custom name/number set in the build pipeline. You can change this naming scheme by editing the release name format mask. In the Options tab of a release pipeline, edit the Release name format property in the General page. Ref : <https://learn.microsoft.com/en-us/azure/devops/pipelines/release/?view=azure-devops#how-do-i-manage-the-names-for-new-releases>.
You can't. release name must be a **unique** name, therefore Azure DevOps requires you to put `$(rev:r)` in the name, because it's adding a incremental number for each release.

Another option is to use `$(Build.BuildNumber)` or `$(Release.ReleaseId)` that are also unique but is not will solve your issue.