Zari seemed to frown when she learned that she was going to be the 1000 wife of Kamdev. But in comics or in the mythology(where he is actually a God) he is monogamous. Here Kamadeva(the person) told that he himself took the ashes of Kamdeva(the God) this means he became immortal(due to divine possession) hence he is being living since ages and his previous wives were dead.
The synopsis states that the Legends travels to 1809 to deal with a magical fugitive. In the episode however, they actually travel to 1802 to do this.