To stop a specific version of an App Engine application in GCP, you can use the Google Cloud Console and gcloud CLI commands. Here are the detailed steps for each approach:

1. Google Cloud Console:
   a. Go to the GCP Console: https://console.cloud.google.com/
   b. Select your project.
   c. Navigate to the App Engine dashboard by clicking the hamburger menu, then click on “App Engine.”
   d. Click on the “Versions” tab on the left side menu.
   e. Locate the specific version you want to stop.
   f. Click the checkbox next to the version.
   g. Click on the “Stop” button at the top of the page. This will stop the selected version.
2. CLI Commands (gcloud):
   a. Install and set up the Google Cloud SDK: https://cloud.google.com/sdk/docs/install
   b. Authenticate with your GCP account: gcloud auth login
   c. Set the active project: gcloud config set project PROJECT_ID
   d. Stop the specific version of your App Engine application: gcloud app versions stop VERSION_ID
   Replace VERSION_ID with the ID of the version you want to stop.

Please note that stopping a version will cause it to stop serving traffic. If the stopped version is the only one serving traffic for your application, your application will become unavailable. Be sure to have another version running and serving traffic before stopping a version to avoid any downtime.