Setting the TF_LOG environment variable to DEBUG causes debug messages to be logged into stdout. 

You add a new resource to an existing Terraform configuration, but do not update the version constraint in the configuration. The existing and new resources use the same provider. The working contains a .terraform.lock, hc1 file. How will Terraform choose which version of the provider to use?

You should run terraform fnt to rewrite all Terraform configurations within the current working directory to conform to Terraform-style conventions.

A Terraform backend determines how Terraform loads state and stores updates when you execute which command?

You modified your Terraform configuration and run Terraform plan to review the changes. Simultaneously, your teammate manually modified the infrastructure component you are working on. Since you already ran terraform plan locally, the execution plan for terraform apply will be the same.