Module version is optional to reference a module on the Terraform Module Registry. If you omit the version constraint, Terraform will automatically use the latest available version of the module

This is what will happen if you run terraform destroy without any flags, as it will attempt to delete all the resources that are associated with your current working directory or workspace. You can use the -target flag to specify a particular resource that you want to destroy.

This is not a valid Terraform collection type, as Terraform only supports three collection types: list, map, and set. A tree is a data structure that consists of nodes with parent-child relationships, which is not supported by Terraform.