Student or Learner
May spelt ever be used instead of spelled in the English Language?
Since you are American, you'll not see it much, but it's perfectly acceptable. I guess the US prefers the regular form 'spelled', whereas either the irregular or regular ('spelt' or 'spelled') are equally accepted and used elsewhere. In these places, it's personal preference/what comes out.
I think 'it's what comes out' is a good summary! I use both. If I think about it, I think I tend to use 'spelled' as a simple past and 'spelt' as a participle: 'At the hotel reception desk I spelled my name out'/ 'My name is spelt with a K'. But this is only a tendency, and I doubt if my usage is consistent.
Yes, there are several pairs like this. One might hope for consistent guidance from a course book, but I remember (though I don't have the book in front of me) that New Cutting Edge Upper-Int introduced the word 'spilled' in the text and then gave the past form 'spilt' in the pull-out 'mini-dictionary' that comes with the book.