I have Lollipop 5.11 (Note 4), and I have the device encrypted.
Will flashing CWM or TWRP or a new software (like Marshmallow) ruin my phone?
I would like to add the device is still not rooted.
Also one more question, is it possible that I can get the decryption key of my phone as a file for emergencies?
What carrier is your Note for? I don't think all US carriers have unlocked bootloaders. I personally nearly bricked my Developer Edition Galaxy S5 because I accidentally left "Reactivation Lock" enabled.
If your data partition is encrypted, I would strongly suggest you take due care and unencrypt it if possible and make a backup of your data before you proceed.
Being a Samsung, I think you will need to use TWRP, but I suggest joining the forums over at XDA. There are a huge number of posts and input concerning rooting and loading custom ROMs over there. It's what they do.
Rick
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