要在两个管道之间创建依赖关系，您可以为第二个管道创建一个管道资源触发器，使其在第一个管道完成时自动运行。例如：

# First pipeline
steps:
- bash: echo "The first pipeline runs first"

# Second pipeline
# We are setting up a pipeline resource that references the first pipeline
# pipeline and setting up a pipeline completion trigger so that our second
# pipeline runs when a run of the first pipeline completes
resources:
  pipelines:
  - pipeline: firstPipeline # Name of the pipeline resource.
    source: first-pipeline # The name of the pipeline referenced by this pipeline resource.
    project: ProjectName # Required only if the source pipeline is in another project
    trigger: true # Run second pipeline when any run of first pipeline completes

steps:
- bash: echo "second pipeline runs after first pipeline completes"

有关详细信息，请参见Microsoft documentation。
对于你的第二个问题，从一个管道传递一个变量到下一个管道，我找到的最好的解决方案是引用和更新管道变量组中的变量，参见文档here。
例如：

# First pipeline 
# As a task in the first pipeline, update any pipeline 
# variables that other pipelines will need

- task: AzureCLI@2
  displayName: Update variable
  inputs:
    azureSubscription: azure-sub-arm
    scriptType: bash
    scriptLocation: inlineScript
    inlineScript: |
      az pipelines variable-group variable update --group-id <<id>> --name <<variable_name>> --value <<new_value>>