there is no code you have 2 unlock it yourself :)
if you are talking about treasure maps, they are used to find treasure...
there is not one sorry
No.
look in the outfit section of your journal and it will tell you what you need to do
In tall trees
Yes.
In Red Dead Redemption 2, the treasure in "Rio del Lobo" can be found in the area around the Rio del Lobo river, specifically near the location of the "Treasure Hunter" side quest. To locate the treasure, players need to follow the clues from the treasure maps obtained during the game. The final treasure is hidden in a cave, which can be accessed by following the river and looking for a small entrance on the cliffside. Once inside, players will find a chest containing gold bars and valuable loot.
Go to the outfits menu in the pause menu and you should see what you need to do in order to unlock that outfit.
You cannot get a gang in Red Dead Redemption, but you can be part of a gang by accepting a wanted poster, then wear the outfit of the gang, then they won't attack you.
If you don't have it already, you can simply purchase it from the PlayStation store, it allows your fame to increase at twice the rate.
Go onto the outfit menu and you will find out what you must do to unlock that outfit.