Two games
Psycho and Forbidden
Both are full games. Forbidden is not a DLC, and you do not buy Psycho first.
Same loop
The difference is intensity and material, not another world.
Psycho
Rating intent · 15
Stylized red and black, a flash. No lasting cruel image. The package has no 18+ content.
The rating is a product intent, not an issued certificate.
Psycho: Forbidden
Rating intent · 18
The same loop, at a higher intensity, where a cruel impression is allowed.
Phones ship only the 15 version. There is no second adult app. No 12 version. The rating is a product intent, not an issued certificate.