Terraform variable names are not saved in the state file, only their values are. The state file only stores the attributes of the resources and data sources that are managed by Terraform, not the variables that are used to configure them.

This is a secure way to protect sensitive data in the state file, as it will be encrypted at rest and in transit2. The other options are not recommended, as they could lead to data loss, errors, or security breaches.

To tell Terraform to stop managing a specific resource without destroying it, you can use the terraform state rm command. This command will remove the resource from the Terraform state, which means that Terraform will no longer track or update the corresponding remote object. However, the object will still exist in the remote system and you can later use terraform import to start managing it again in a different configuration or workspace. The syntax for this command is terraform state rm <address>, where <address> is the resource address that identifies the resource instance to remove. For example, terraform state rm aws_instance.ubuntu
[1] will remove the second instance of the aws_instance resource named ubuntu from the state.
References: Command: state rm : Moving Resources

The terraform state file is locked when a Terraform operation that could write state is in progress. This prevents concurrent state operations that could corrupt the state. The forbidden actions when the state file is locked are those that could write state, such as terraform apply, terraform destroy, terraform refresh, terraform taint, terraform untaint, terraform import, and terraform state *. The terraform validate command is also forbidden, because it requires an initialized working directory with the state file. The allowed actions when the state file is locked are those that only read state, such as terraform plan, terraform show, terraform output, and terraform console. References = [State Locking] and [Command: validate]

You do not need to use different Terraform commands depending on the cloud provider you use. Terraform commands are consistent across different providers, as they operate on the Terraform configuration files and state files, not on the provider APIs directly.