When a GET REST API request is sent without valid authentication, the server typically responds with a 4xx status code, such as 401 Unauthorized, and does not execute the request. This ensures secure access and enforces proper client authentication before any operation is performed.

IGMP V3 is compatible with V1 and V2 (and obvious V3), likewise, IGMP V2 is compatible with V1 (and obvious with V3). Finally, IGMP V1 is only compatible with V1.

The applet is missing the trigger event configuration. In this case there is no trigger event, so none must be selected. The access list is already configured, the applet only needs to apply it.
event manager applet Block_Users
event none
action 1.0 cli command "enable"
action 2.0 cli command "configure terminal"
action 3.0 cli command "interface GigabitEthernet1"
action 4.0 cli command "ip access-group 101 in"
action 5.0 cli command "ip access-group 101 out"
action 7.0 cli command "end"