After a multicast transmission has begun, what option causes connected clients to finish the install, but prevents new clients from connecting to the transmission?

The option is "Deactivate".

Explanation:

If we use the option Deactivate after the option Deactivate the transmission, the users are already installing will continue with the installation.

If a new user wants to connect with the transmission, the option Deactivate prevents those connections.

When the installation has been completed, the transmission will be eliminated.

If we don't have any client before to use the option Deactivate, the transmission will be eliminated automatically.