Check if an Azure VM is already up and running

I want to start a vm using rest api following this code https://docs.microsoft.com/en-us/rest/api/compute/virtualmachines/start

But have 3 questions

1. Is there a way to know if a VM is up and running already using API or any other code?

2. What will happen if I try to start a vm which is already running?

3. How can we find out after calling the API that the VM is actually up and running? Is there a fixed wait time?