1] volume range is 00…40 (hex) because of legacy support.
This is going to be changed to 00…7F in the near future.
By the way, MIDI instruments already have a 00…7F range.
At the moment, values greater than 40 (sample/VSTi) or 7F (MIDI) are ignored
2] some of panning column values are reserved for specific uses: values 90, 91 and 92 are used for MIDI/VST purposes (check manual)
3] this needs a long reply: trackers work with “ticks” internally. The rows you see in the pattern are made of ticks. The number of these tick for each row depends on the “speed” parameter, which can be adjusted on the GUI or by using F1xx command (xx is the new speed value); for example, F10C says to ReNoise that next rowse will have 12 ticks internally. The pitch command, i.e. 010A, says to ReNoise to add 10 pitch units for each tick. Then, the more the speed value is, the more the command has effect on the pitch. 01xx is pitch up, 02xx is pitch down
4] volume slicing (04xy) turns volume on and off inside a row. The x value tells for how many ticks should be turned on, the y tells how many ticks the volume should be turned off.