http://www.dotmasr.eg/Files/GeneralPolicy.pdf
it is very confusing indeed about what to do with many typos and letters
anyhow , here is the beginning when arabic natives start to think and organize things about IDNs
for now rules (which may be changed or modified later as they say )!:
1. only arabic letters accepted
2. No space between words
3. minimum three letters
4. maximum 63 letters
5. dash is not accepted in beginning or end
6. double dash like (--) is not accepted
7. pronounciation symbols are not accepted
8. numbers are not accepted in beginning or end ( may be at the end later .. not now!)
9. it is accepted to register numbers only ( when you register arabic numbers you will be given a free registeration of english numbers as well)
10. when you register a word with the letter ى you will be given free registeration of the word with the letter ي
in the pdf file a list of accepted letters
regards
Gee