A difference in leg length will not effect your brain health. You can easily get a heel wedge to balance your leg length. There are more extreme ways to balance leg length but there is no reason to consider them nor worry about your leg length being an issue with your brain health.

What makes you think your concussion and puberty have a relation to the other concepts ? What is wrong with your knee ?

It would be worthwhile to ask your doctor for a referral to an orthotic specialist to make you a wedge. It will help your hips to stay healthy by resolving/reducing your limp.