User blog comment:Furkan Zomer/Possible Solution - Cursed BBI Weapons and Armor lv.3/@comment-10707282-20130703010848/@comment-3068131-20130703045243

To answer your questions,

Yes if your 4th weapon lv.2 is the kind of weapon of what you need the 4th weapon lv.3 will the correct weapon so thats correct, yes you purify 4 weapon lv.2's and 4 weapon lv.3's at the same time, usually the first is also the same kind of weapon as the weapon lv.3.

And yes you have to search for more LV.2's until you get the "saphire daggers" or the other one.