Once plugins are installed, you can now scan up to 16 IP addresses simultaneously (e.g., 192.168.1.0/28). To scan more hosts, you would need a commercial license.
Yes, many universities provide access to Tenable's Academic program. However, individual students can still use Nessus Essentials for free. nessus license key free
Technically, the key is single-use, but you can request a new key for each personal device. For lab purposes, you can also run Nessus in a virtual machine. Once plugins are installed, you can now scan