Can my piece be touching corners of an other color's piece (besides my color's corners)?

I have seen them made out of plexiglass and other types of plastics. Basically any hard and smooth material can be used to make a puzzle box.

Baby oil and olive oil are alternatives that work well. Vaseline is not recommended as it can damage the fretboard with constant use.

Yes, you can use peanut oil or rice bran oil. Use your favorite cooking oil!

Let it sit or blow on it or put a cold towel over it.

Any acrylic paint or fabric paint should work.

It depends. If it is the back of the knee, that is good - you are stretching. If it's the front, stop, and maybe go see a doctor.

Get a new boiler or exchange it for a higher boiler or put a protection cover on all the pipes. It is also important to tell them not to touch...

The ball cannot be snatched out of a players hand if they clearly have it in full grasp.

Their bodies should be facing the opposite lineup, but their heads can be turned towards the basket.