If a Nartaki or any other multi-limbed 4-6 arm having metatype uses several guns at once obviously they split their dice pool among the extra limbs, however I have a few questions:

1. Can they mingle Complex and Simple actions together (BF/FA with one hand, SA with the other).

2. Since Suppression fire doesn't allocate recoil how do you handle it when two arms are suppressing while the other two are pumping SA shots with no recoil penalty? Doesn't that seem odd?

3. Is suppression fire considered an 'action' in which the subject must split their die pool?

I'm confused on how this works so a bit of enlightenment will be much appreciated.

There's no RAW for this. You'll have to work out a compromise with your GM. I would suggest the following, if one of my characters wanted to do this:

1. Spend the largest action type. You can FA with one hand, and all other three get one SA attack as part of that, with fully split (4 ways) dice pools.
2. Just leave it as is, even if the recoil seems odd. Lots of people will have different theories on this, but c'est la vie.
3. Yes. However, I'd split it in the number of ways doing different things. For instance, if you're SA shooting two dudes and using two machine pistols to suppress the same target, I'd split it three ways and use the rules for minigun suppression (since you're shooting a comparable number of bullets). Suppressing two different areas and shooting two dudes would be a 4-way split.

Underneath, though, it just requires some creativity and compromise between you and your GM.