No, these are actually referring to the gyroscopic sensors on the spacecraft. This article [0] makes it a little bit more clear. While there are actuators that use gyroscopic torque, referred to as Control Moment Gyros (CMG) Hubble uses reaction wheels for pointing the spacecraft.
No, the comment you're replying to is confused. These gyroscopes are entirely used for determining Hubble's orientation. Reaction wheels effect the actual rotation, and Hubble's are fine.
I think the confusion is a result of imprecise language talking about how they are used to slew the telescope. They are "used" but as feedback, in conjunction with other systems. Also, there have some prominent reaction wheels failures on other missions, and that contributes to the confusion.
No, accelerometers detect acceleration in linear direction (up/down, left/right, forward/backward), while gyroscopes detect rotation (pitch, yaw, roll). Smartphones have both, to detect all six degrees of freedom.
Edit: Apparently, for smartphones, all these sensors are integrated into a single MEMS chip, one sensor for each degree of freedom, three accelerometers and three gyroscopes: https://youtube.com/watch?v=9X4frIQo7x0
[0] https://science.nasa.gov/mission/hubble/observatory/design/h...