Contrast Fomentation (Hot and Cold). Avoid Squatting- Avoid sitting Cross legged

Please give a brief account of mode of injury. Instability per say is attributed to ligaments usually ACL. Though flipping meniscus can give feeling of instability.

You have an old meniscal injury and a clicking sound in the knee. In such situation, it will be more appropriate to check your knee to identify which part of your knee is generating the clicking sound. In addition, it will be helpful to have a look at your scans too. a partial thickness, grade 1 or grade 2 tear is unlikely to need surgery. but a bigger tear should be treated by arthroscopy, because if left untreated, such tears increase with time and likely to cause problems with knee later

Strength exercises in gradually process

Do daily exercises. No need for surgery.

You should go for knee arthroscopy and address the problem since it's a chronic tear and you are having symptoms of clicking and pain. If left untreated for long duration it can cause cartilage damage.