Question

Select the sentence that is punctuated correctly. if i use a pattern in the use-first range, it is considered dominant and i begin my learning with that pattern. if i use a pattern in the use-first range, it is considered dominant, and i begin my learning with that pattern. if i use a pattern in the use-first range it is considered dominant, and i begin my learning with that pattern

Answer 1

The sentence that is punctuated correctly is definitely the last one :  if i use a pattern in the use-first range it is considered dominant, and i begin my learning with that pattern. As you can see, ''and'' is a conjunction which joins two independent clauses which means that you should put a comma before the last clause.
Hope that helps!