Oxygen os to cyanogen in one plus one

Hi.. i m using one plus one.. I had cyanogen mod when i bought the phone.. The customer care representative then upgraded it to oxygen os. I want the cyanogen mod back but factory reset is also coming to oxygen os. Can i upgrade to thus latest cyanogen mod version without harming the phone or i have to stick to oxygen os only?? Please advice

Oneplus 2 Oxygen OS ringtones

Hey all!! I wanna ask if someone can post me a link to the stock oxigen os alarms, ringtones, ...

Thanks for help :)