how to change between weapons that u dont have the req for them

hey guys i saw some ppl changing from kats to clups or whatever weaps that need str and they have 0 str then change back umm dont mean they change by restarting and so i mean they change in arena while they are moving like when nij wear lvl 70 bow in rb so ... oh and water between BS and spear anyone can help me with that ??

A lvl +70 1st RB or above character can use any other class weapons as long as they are level 70 or less, a 1st RB level 71 ninja can hold a level 70 BackSword, a level 71 1st rb monk can hold level 70 katana, etc.