Puzzles

21 possibly, he blocked the window from the outside, but it remained square from the inside
22 2 3 6 years
25 those who wanted to get married often opened it to check if it was boiling or not; the air temperature in the kettle would drop at that time. But the other one didn't care, and she didn't open the kettle.
26 Take one coin from the first hat, two from the second, and so on. Then, the difference in grams will be the weight of the hat.
29 one divides the piles, the other chooses which one he wants.