All iPads: Verizon data on iPad only (phone on another carrier)

[davideotape]

Crowd-sourcing this a bit because nobody at Verizon seems to know for sure or can give me a straight answer with any bit of confidence. Sorry if this is a bit redundant, but at least it's not another iPad mini/Retina display thread, right? and this is trying to drill down a bit more from other discussions.

Anyway, anyone have this who can walk me through the pricing here? as I understand it we've got
Prepaid:
$20: 1gig
$30: 2 gig
$50: 5 gigs
$80: 10 gigs.

Share Everything:
$40: 4 gigs ($30 for 4 gigs and $10 "Share Everything")
other tiers of share everything.

Questions around Share Everything:
Q1: Can you upgrade your plan within the same month? Can I go from $20 1 gig, then when i'm about to hit the 1 gig, move to the $30 to gig, or do i have to pay an additional $20 to get an extra 1 gig?

Q2: Can I move from a prepaid plan to a Share everything plan?
Q2a: If yes, can I do that within the same month? Or do I go Share Everything one month, Prepaid the next?

Question about process/logistics:
Q1: I can go month to month, cancel it one month, order it the next. Can I do this directly from my device, or do I have to call?

Q2: SIM CARD non-use issue: wassup w/that?

Q3: I have a Sprint ipad Mini right now but i'm within my return window. Would I HAVE to bring this thing back and buy an entirely new iPad mini, or could I just cancel my Sprint service, hit a few buttons, turn a few screws and voila, have a Verizon device?

THANKS!!!

feel free to make this a catch-all for Verizon Q's as well.