We have this scenario, an active survey. We would like to changes structure without losing previous answers.

I worked through a process to keep the survey active and makes changes to a copy of the survey. Then import responses and participants into the new survey copy from the active survey.

I am aware you must activate the survey before you can import responses and participants.

My questions are:
Is there data integrity issues with exporting data from the original survey to import it into the new survey?

If so, what are they?

I would like to the survey downtime as small as possible.

Can the end user update their old answers to a survey?

Are you using VV format, right?

If question codes are kept the same in between surveys, there should be no problem.

Also, if using it, you should take care of tokens as well.

I would recommend running a rehearsal and doing a backup as well.