Can I clone and edit existing surveys?

Yes, this feature is an option on all plans except the Free plan.

1. On the main navigation panel expand the Surveys menu, then click on > Manage Surveys.
2. Once you have a survey saved you can duplicate and edit it by clicking on the Clone from Existing button in the top right corner of the Manage Surveys page.

See this article for more on creating an survey from an existing one.