The M9's (non Looper) functions can be MIDI sync'ed to an external MIDI time clock, yes.

To clarify, a specific example would be to be using a Delay effect, where the Tap tempo value is constantly "refreshed" every measure from a sequencer program from a laptop that's generating a MIDI event on the "1" of every measure. This ensures that the Tap Tempo is in sync to the sequencer software.

Your question, however appears to be focused on the M9's sound-on-sound Looper, which is a very basic loop buffer.

1. No, you cannot set a loop length in advance sorry. The loop length is set by the physical recording of the first pass/take. You also only have up to 28 seconds of loop time (in Mono).

This isn't like a software program such as Ableton Live where you pre-define the amount of looping segment. It's not that advanced.

2. Similar to my answer for #1, there's no audio quantization whatsoever on this Looper. It's a WYRIWYG (what you recorded-in-reality is what you get) sound-on-sound looper.

In order to do those two tasks, you're better off using a software-based loop program that focuses on those features.

The M9 Looper is a secondary function of the unit, really. It's great for spontaneous "sound-on-sound" interludes or intros that can be created on the spot. Think of it like an ambient soundscape delay. Or, a simply practice tool (record a riff, play in back and practice soloing on top of it). Those 2 examples are what the M9 Looper can do well.