止痛藥問提

Your question is missing an important parameter. The weight in Kilogram of the person is missing. The weight is more important than the age. A 12 years old weighing 50kg and one weighing 35kg is different.

Question 5 can be answered, but the best analgesic depends on which type of pain.
The prefered drug for Menstrual pain --- Mefenamic Acid is mostly preferred.
Headache-- paracetamol is sufficient (depending of types of headaches)
Muscle pain/Skeletal pain -- NSAIDs are regarding superior to paracetamol.

There is a pain ladder (just for your information), according to the efficacy of analgesic.
1. Paracetamol.
2. Non-Steroidal Anti-Inflammatory Drug (NSAID) including mefenamic acid, ibuprofen, nimselide and more..
3. Weak Narcotics. ex. Doloxene/Dologesic
4. Strong Narcotics ex. Morphine