Board Thread:Questions and Answers/@comment-25309891-20150504175002/@comment-25386610-20150504203140

If you register your email and log in with that, it should be fine.

However, I think you lose your Crystals (idk about coins) but your levels, pets, cookies, treasures should all be fine.

Edit: Yeah it should be for line. It just erases chat history/etc on your old phone so that you're logged in on only 1 device.