Explanation

Box 1: No
User1 will receive the two alerts classified as medium or higher.
Sign-ins from infected device is classified as low. This risk detection identifies IP addresses, not user devices.
If several devices are behind a single IP address, and only some are controlled by a bot network, sign-ins from other devices my trigger this event unnecessarily, which is why this risk detection is classified as Low.
Box 2: No
User2 will receive the two alerts classified as medium or higher.
Email alerts are sent to all global admins, security admins and security readers Sign-ins from infected device is classified as low. This risk detection identifies IP addresses, not user devices.
If several devices are behind a single IP address, and only some are controlled by a bot network, sign-ins from other devices my trigger this event unnecessarily, which is why this risk detection is classified as Low.
Box 3: No
User3 will not receive alters.
Email alerts are sent to all global admins, security admins and security readers.
Reference:
https://docs.microsoft.com/en-us/azure/active-directory/identity-protection/overview-identity-protection
https://docs.microsoft.com/en-us/azure/active-directory/identity-protection/howto-identity-protection-configure-r