What has a ring but no finger?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

Move three sticks of the spiral below to form a square.

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

Its something that each of us devours,
Not just us but birds, beats, trees, and flowers,
Frets iron and nibbles steel,
Toil hard stones to meal,
Exterminates king, collapse town,
And blows the mountains down.

Find the hidden panda in the image below.

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

Jim and Sarah are in a long-distance relationship. Jim buys an engagement ring for Sarah and wants to mail it to her. Unfortunately, the only way to ensure the ring will be received is to place a lock on the package. Jim has locks and Sarah has locks, but neither has keys for each other’s locks. How can they make sure the ring isn’t stolen?