You should be applauded for being so industrious. No one at uni will get cross at you for reading ahead and preparing your assignments. Note, assignments may change each year to stop second years selling their first-year assignments. Hence the assignments you have already completed would have been good practice but may not be the actual assignments for you when you repeat the year. Even if they are the same, so what, you have not cheated; its all your own work. You have just got ahead of the curve.