If it works alone and not working along with other sensors, the problem may be of the I2C addresses conflict. Check to see if there are two modules on the same I2C address.
Check the power too. Do all your modules get the power they need?
Linear Acceleration at given axis = Actual Acceleration - Gravitational Acceleration
Gravitational Acceleration across any Axis = Magnitude of Gravity Vector x Cosine of axis angle with the Gravity Vector
The temperature sensor is likely included to keep the gyroscope and accelerometer better calibrated over the specified temperature range. The temperature may not be the ambient temperature should the chip warm up.
The temperature sensor specifications are in section 6.3 on page 14 of the specification sheet indirectly pointed to in the question.