To answer your questions:
1. It takes about 9 months for the reconstructed ACL to bind itself firmly to tibia and femur. This means it cannot be stressed fully before 8 - 9 months.
2. Essentially precautions relate to avoiding any stress that is likely to rupture the reconstructed ligament. This could be a break at the binding site or break through the substance of the ligament. Therefore, all sports activities where you need to bend your knee and pivot around your leg should be avoided. If you are not an athlete then common activity like driving a motor cycle or a scooter should be avoided.
3. Menisci function as washers that absorb shocks at the knee. This has a protective function on the cartilage of the knee. Therefore, removal of meniscus is likely to lead to early degeneration of the knee.
4. If the reconstruction is successful, then it should last you all your life. Unless, you get injured again.
5. Regular quadriceps exercise is the best way to protect your knee.
6. As far as I am aware, glucosamine does not protect your knee or heal degenerating knees.
7. I am sure you could look up google search on problems of the knee. There are sites that are related to specific joints or general sites related to specialty of Orthopaedics. Try www.kneeshoulder.com.