To make it short, yes it’s very secure and you CAN undo it, I’ve done that several times to verify that you can move the account to foreign site and back again
Step by Step How To Move A Kindle Account
1. Step Log into Amazon.com
2. Step Click on Manage Your Kindle on the Kindle support page (it’s in the box Self-Service)
3. Step Scroll a little down, in the left sidebar you see a link Country Settings
4. Step Then click on Change and select one of the pre-existing foreign adresses and click Update
5. Step You will be warned. My recommendation is to make sure you speak the language of the Amazon site you’re transfer your account to. If you don’t it will be a bit tricky to move the account back without help from Amazon support
6. Step Done – you have successfully moved your account
7. Step To undo the move and move your account back to Amazon.com you will have to log into the foreign site and repeat the steps. The menus are VERY similar, but they are not 100% identical, so check the options carefully
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