Installing a custom ROM

[molevi]

Hello everybody,
I have the OnePlus One with Cyanogen OS (12.0-YNG1TAS2I3) installed on it.
I want to install a custom ROM.
Is it possible to replace a ROM without rooting the phone?
If not, is it possible to restore a phone to be completely unroot again after rooting it (for a situation I want to sell it)?
Thanks for your help.

 

[ceo_rakoun4]

You can change a ROM only on a rooted phone. As for the second question there are some videos and articles online that show how to unroot your phone but i have not tried it myself to know for sure..

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