Is it Cliff Weapon quest is still available as of now?
Yes, only available once. If you finished it already then you cant accept.
As far as I know, it's still available. It's for once per family - you'll see six (6) different quests due to the level of your characters but you only can complete three (3) of it whoch is for the main weapon, sub weapon and awakening weapon. You need to complete the main quest from the beginning until the end of Calpheon's storyline.
If you're a returnee, you can't do the quest again if you done it before.
link info for cliff quest https://www.sea.playblackdesert.com/News/Notice/Detail?boardNo=2971&countryType=en-US