Hi, I have a lab quiz tomorrow on this lab attached, but we didn't get time to go over it, and I am not really sure how to answer the last two questions on the post-lab (analysis questions #3, and #4)

My second question is how does the indicator phenolphthalein get returned (reversed) to a clear milky solution when HCl reacts with the indicator and Ca(OH3) which was originally pink?

Thank you so much!

   

Q4
Mg >Zn>Cu
Mg can displace Zn metals from its compounds and Zn can displace copper from its compounds. However copper can not displace Zn or Mg from its compounds.
Mg is alkaline earth metal so more reactive as it has more tendency to lose electrons.
Zn is more reactive than Copper because it can give 2 electrons easily and  get a stable configuration of 3d¹⁰. 

For Q 3
Mg is very reactive and reacts with oxygen of the air to form an oxide layer on its top.
May be due to this no reaction is visible with Zn(NO3)3.