Which of the following are homogeneous in nature?

While diluting a solution of salt in water,a student by mistake added acetone (boiling point $56\,^oC$). What technique can be employed to get back the acetone? Justify your choice.

The concentration of a salt solution in terms of mass by mass percentage is $20 \%$ and the mass of the solution is $550 \text{ g}$. Determine the mass of solute present in the solution. (in $\text{ g}$)

$(a)$ $7\, g$ of iron filings and $4\, g$ of sulphur powder is treated with dilute sulphuric acid at room temperature. Name the gas produced.
$(b)$ The same mixture is heated strongly,cooled and then treated with dilute sulphuric acid. Which gas would be produced?
$(c)$ What is the cause of this difference in results of chemical reaction in different conditions?

Colloidal solution appears to be homogeneous but actually it is heterogeneous. Give justification for this statement.

$(a)$ $A$ sugar syrup of mass $214.2\, g$ contains $34.2\, g$ of sugar. Calculate the concentration of sugar in the syrup.
$(b)$ What is a solution?