I could be wrong but I think one is a misspelling. Nerelisin(iz) is the correct one

"Nerelesiniz is a mispelling." Formal : "Nerelisiniz is correct." Exact meaning is 'Where are you from'. You can also say "neredensiniz". Informal : "Nerelisin is correct" Exact meaning is 'Where are you from'. You can also say "neredensin".

Thanks for these details....I truly appreciate your help.

Nerelisiniz is okay, for the second i think you wanted to type Neredensiniz. mainly, both have same meaning. For better information, I could say: Nerelisiniz refers to "from" Neredensiniz refers to "whereabouts" in english