2. Function

No they aren't. Most of them are actually passive. With an active pickup there is a built-in preamplifier installed in the guitar that ensures noise-free operation and a low-impedance signal which won't diminish regardless of the length of the signal path / cable length.

Depends on what you want really, these will be DiMarzio pickups with a weaker magnetic field, resulting in lower output but a more sustained and dynamic sound.

F-spaced pickups were created specifically for use with guitars that have Floyd Rose tremolo systems installed. The distance between the two poles is a bit more ample and, as with standard pickups with standard systems, this guarantees the best detection of the individual strings. Depending on the manufacturer, this design is also called a trembucker.

A MIDI-pickup is needed in order to transfer analog data, such as that received from strumming a guitar, to an interface which then converts the information to MIDI data. With MIDI data a synthesizer can play any imaginable sound, this means that there is the possibility to reproduce guitar sounds on a keyboard, for example.

Reverse Wound/Reverse Polarity pickups are single coil pickups designed specifically for use in the middle position of guitars with a typical 3 single-coil set-up. The coils of RWRP pickups are, as you may imagine, wrapped in reverse and the magnet's poles are reversed in comparison to the standard pickups. This is so that they can be connected with both the bridge and neck pickups to give that typical humbucker effect.

Yes! They even have a special name, ''stacked'' pickups. With stacked humbuckers the coils are placed one over the other, rather than side by side. This way they still have the same look as a single coil pickup.

To give amps more power and produce better distortion you can install high distortion pickups which have an especially high output power, helping the amp along so to speak.

Two pickups which are in phase will sound normal - full and clean. Out of phase humbuckers sound thin and nasally. The reason for this is that all the bass and mids get swallowed up in this mode.

To explain the effect better we can use an example with speakers: when a sound is simultaneously transmitted through two loudspeakers that are working "in phase", it is bold and loud. If the speakers are out of phase the membrane of one speaker moves forward while the other moves backwards. Resulting in a thin and quiet sound.

To create the out of phase sound two connected pickups work, in simplest terms, against one another. This causes the frequencies to cancel out, giving a thin and piercing sound.