I know next to nothing about widevine decryption so forgive my ignorance - I was wondering if I download protected files now and get a widevine key later from another device, would I be able to decrypt the file with that key? or must the decryption be done with the same key/device that was used to download the file?
Method should still work for L3 decryption. L1 decryption is hardware based instead of software based and afaik not possible to crack yet.
Ah, I had the numbers backwards. Is L1 heavily in-use?
Yes. Depends on the platform. For example with Netflix L1 is required for full HD, L3 will only give you access to SD content.