This Seeking Tech tutorial will show you how to unlock the Old Snake, New Tricks trophy and achievement in Metal Gear Solid Delta: Snake Eater.
To get this, you need to “start a game in Legacy Style.”
In order to do so, start a new game and then select Legacy Style when you are asked to select a Play Style. Afterwards, complete the rest of the settings to unlock the trophy and achievement.
You can check out the video guide below for additional help: