Can this item control both humidity and temperature at the same time?

It only control the temperature, not the humidity.

Can the temperature probe be directly put into the water?

Yes the temperature probe can be directly put into the water

How to turn ON/OFF the Buzzer?

Can turn on/off the buzzer by long press the the down key.

If you cannot add your Smart Device , please check:

1) Whether the Device is powered on.

2) Whether the phone is connected with 2.4GHz WiFi.

3) normally you can manually press and hold the

power button for 3-5 seconds. If the WIFI icon on Screen flash 3 times

per second,it is ready for configuration

If you cannot add your Smart Device , please check:

4) Setting up Wi-Fi router: setting encryption method as WPA2-PSK and authorization type as AES, or set both as auto. Wireless mode cannot be 11n only.

5) To stay strong WiFi

6) Whether connected devices have reached the maximum number of the router