How was my communication with you during the process?
It was actually good, what you can actually do is ask to if there was something that needed changing, and they y'know forgot something. an additional question "anything missing from this sketch?"
but there's 1 thing, you should ask if there is any optional features of a character, say like Roy's wings for example. they're optional but is included in the original design.

Were enough updates provided? (Sketches, inks, colour roughs)
[I've tied the answer with question 1's answer]

Was the time reasonable?
The timing was incredibly good too, though breaks possible due to life, but that's understandable. just make sure you let the commissionee know that something has come up in your list of things to do.

Was the end product to your satisfaction?
The end product is actually very nice! what i can suggest is how you shading things, but in all reason it's still very detailed for what it is.

Any suggestions for how I could do things in the future?
[Answer sort of tied to question 4, suggestion here]
What you can do with the shading is use at least 2 layers for shading, like a light shading and a deep shading layer, and work from that.

Would you recommend me to your friends?
I would recommend them to you because you've progressed well ever since i saw your art at first glance, it's very good and is a lot better to this day.

How was my communication with you during the process? Very clear
Were enough updates provided? Yes
Was the time reasonable? You were a lot faster than I expected.
Was the end product to your satisfaction? It was wonderful minus that one detail that you fixed right away.
Any suggestions for how I could do things in the future? none
Would you recommend me to your friends? Yes.