Can you break open a sealed barrel to get food on Shabbat?
Breaking a seal isn't "making" something — it's destroying. Since it's destructive (not building or creating), it's permitted when done to access food.
Question 2
Is clapping hands or dancing forbidden on Shabbat?
The Sages' concern: musical activities might lead to fixing an instrument (which is building/makeh b'patish). Note: many later authorities permitted clapping and dancing for mitzvah purposes.
Question 3
Can you read business letters on Shabbat?
The Sages forbade reading business documents, accounts, and similar material. Shabbat should be a complete mental break from commercial life.
Question 4
A fire breaks out Saturday afternoon. How much food can you save?
Saturday afternoon: one meal remaining. The rule is proportional — you save food for the meals still needed. Friday night: 3 meals. Shabbat morning: 2. Afternoon: 1.
Question 5
Can sacred texts (Torah scrolls, etc.) be saved from a fire on Shabbat?
Sacred texts get special treatment. Even a worn Torah scroll with only 85 readable letters may be saved from fire on Shabbat.