How does the Terraform cloud integration differ from other state backends such as S3, Consul,etc?

You have created a main.tf Terraform configuration consisting of an application server, a database and a load balanced. You ran terraform apply and Terraform created all of the resources successfully.
Now you realize that you do not actually need the load balancer, so you run terraform destroy without any flags.
What will happen?

What is the Terraform style convention for indenting a nesting level compared to the one above it?

Which command add existing resources into Terraform state?

When should you write Terraform configuration files for existing infrastructure that you want to start managing with Terraform?