Normally it is not necessary to calibrate the IMU as the calibration operation is performed before sending the product. However, if the sensor falls or receives a strong shock, it may be useful to recalibrate it. To learn more, watch the dedicated video tutorial.
The HAPPY Q application and thus QField requires an internet connection to access the correction systems (NTRIP). However, the SIM card is not installed in the sensor but in the connected phone or tablet.