1.0 Accessing VM guest from host
After installing VirtualBox, it is possible to access host from the guest, but not vice-versa. The user is not able to do SSH access into the guest from the host. The host is Ubuntu Linux desktop 20.04 and the guest OS is Ubuntu Linux server 20.04.4.
The problem was resolved by changing the network settings for the VM. Click on the relevant VM tab and then click on Network to get the network settings. For "Attached to: " choose, "Bridged Adapter". Under name, select the network interface of the host, which is configured to communicate with the router. Since in this case the host was communicating using the WiFi, and interface name for that was wlp3s0, the same was selected.
Next, click on Advanced. The Adapter Type chosen was PCNet-FAST III (Am79C973), Promiscuous Mode was Deny and Cable Connected box is checked.
When the VM was booted, it was possible to SSH form the guest to the host and vice-versa. In the default window for the VM, mouse, clipboard, etc. do not work. However, on opening a new terminal window on the host and doing a SSH connection, mouse and clipboard can be used from the terminal running the SSH session.