There is a big problem. Without the Internet triggers and timers on raspberry3 not work. If you turn off the Internet and does not work a timer or trigger a fire or a flood can occur

Yes, this is one of the limitations of cloud hosted IoT. It is always recommended that you do not rely on Cayenne to control critical applications such as the ones you listed. With Arduino you can code in your own fail safes but currently it is not possible with the Raspberry Pi. That is going to change soon as the MQTT release is entering its final stages.