Does Apple Lossless Audio Codec (alac) encoded m4a work like an iPhone ringtone? If not, what are the supported audio formats for iPhone ringtones?
Note that the .m4r file is actually the same format as the .m4a file, so you can simply rename it to .m4r and drag it back to iTunes.
m4a won't work as iPhone ringtone directly. There is only one audio format for iPhone ringtones and that is .m4r
ITunes ringtones are normal .m4a files, but they should be exactly 30 seconds long. (And they must have a .m4r extension even though the file is a standard .m4a file)