Enter your student code and the public address of your load balancer: an IP address or a DNS name, nothing else (no http://, no port, no path). Every check is recorded with its own code; nothing is overwritten, and you can check as often as you like.
Assignment 3 checks the same five things as assignment 2, and one more: every machine reaches the database, and the database's address is inside the database subnet. The beacon must be the a3 image, started with DB_TARGET=<db host>:5432. When those six are green, the last step is to upload the Terraform files that built it.