These are two different sentences and you already mentioned that the origional sentence had a comma splice, so option 1 is incorrect. A semicolin can always be used for joining two complete sentences, so option 2 is correct. These are two complete sentences, so option 3 is definitely correct. Option 4 has a sentence that has two complete sentences joined together without any puncuation, which is incorrect, so Options 2 and 3 are correct.
