As the title says, how do u upgrade items? i see some items saying ungraded, what sort of materials do i need to upgrade to make it have extra stats? can someone please tell me how do u do this please?

Fortifications to upgrade (south of the sqaure). And for ungraded, you go to the place (south or southeast of the sqaure) and I believe you grade it (having extra stats).

any specific item to grade an item?

i know how to upgrade but i dont know anything about how to craft stuff.. anyone have a detailed guide on how to craft stuff and what is the use of the crafted items?

also i want to know the lvl of items like which are the rarest etc.. and for those rare/unique items during upgrade will they fail? do they have any safety cap up to +?? just want to make sure so i wont break my item during upgrades.