Answers:
Question 1: 3 sig figs
Question 2: 4 sig figs
Question 3: 5 sig figs
Question 4: 8 sig figs
The rule for sig figs:
Any number after a zero in a decimal is one sig fig.
Example: 0.00359, it has three sig figs.
Also, remember if there are zeros after a number greater than zero, it is also a sig fig as well.
Hope this helps you!