They all sound fine. Just to clarify, it's spelled "understand".
Here are some other ways to say, "Did I get it right?"
Neutral / Common:
Is that right?
Is that correct?
Did I understand correctly?
Am I right?
Casual:
Did I nail it?
Did I get it?
Got it right?
That sound about right?
Polite / Formal:
Have I understood that correctly?
Is my understanding correct?
Would that be accurate?
Clarifying / Reflective:
So, just to check—did I get that right?
Let me see if I got this straight…
I just want to make sure I got it right.