Question: how to set a custom ringtone for a contact on iphone?
Answer: Pull up a contact you'd like to set a custom ringtone or text tone for (either in the Phone or Contacts app)
Tap Edit in the top right corner.
Tap on Ringtone and then make a selection, tap Done to set the ringtone.
Tap on Text Tone to set a custom option, make a choice and tap Done.