Q1: Do these swim trunks have mesh lining?

Yes they do. The mesh lining is very soft. Don't worry see through and scratch the secret parts.

Q2: How long are these swimshorts?

About 20.8 Inch (size 28) To 23.7 Inche (size 42). They come to the knee, covering about 1/2 the knee.

Q3: Do these trunks have pockets?

Yes, double side with deep pockets and a side cargo pocket on the right with a flap that is secured with Velcro.

Q4: Does the closure string go all around the waist? Or just fake in front?

It goes around the waist, so you can tighten them.