1. Should you use apostrophes with possessive pronouns? No. Possessive pronouns (such as his, hers, theirs or ours) do not use apostrophes.
  2. Can you end a sentence with a preposition? Sure, if you want to. Although, in some writing contexts it is frowned on.
  3. Is this sentence in the active voice: 'I eat chocolate'.  Yes. The 'doer' (subject) is placed before the predicate ('eat chocolate').
  4. Which is correct: 'the cats' pajamas' or 'the cat's pajamas'? Both, but for different numbers of cats. Cats' pajamas (many cats) or cat's pajamas (one cat).
  5. Should you include a full stop after 'Dr'? In Australia, usually not. In other places, such as the US, you might.
  6. Which of this tricky homophone pair is correct: 'Sandra needs to practise/practice riding her unicycle more often'? In Australia and the UK the verb is 'to practise', in the US it is 'to practice'.
  7. Can you use commas and semicolons interchangeably? No. Flat. Definite. No.
  8. Is there a difference between a dash and a hyphen? Yes. In looks and purpose. In fact there are a few types of dashes.
  9. Can you accurately identify which of these questions are about language rules and which are matters of language style? Well, that's for you to decide.
  10. Do you know where to find reliable sources to answer these questions?  If not, I can suggest a few user-friendly places to start.

Photo: The top of the Brooklyn Bridge, New York, New York