5.Do you know you can use toothpaste to close or seal the envelopes?
Yes. Just some a very small amount of toothpaste on the edges of the envelope and it will work like a glue.
6.Did it ever happen with you that you accidentally wet all your match sticks and then the match sticks would never work after that?
In such cases, just wipe the match sticks using a cloth and then rub some toothpaste over the place from where it lights up. After doing that you would be able to light your match sticks once again.