Here is the full list of all 5 Cactus Simulator 2 achievements.
Be a cactus for 1 hour (Score 3600)
Be a cactus for 5 hours (Score 18000)
Be a cactus for 10 hours (Score 36000)
Be a cactus for 50 hours (Score 180000)
Be a cactus for 100 hours (Score 360000)