Give Reasons for Each of the Following Experimental Techniques Used

Give reasons for each of the following experimental techniques used in crystallization.
(a) A hot crystallization solution is not filtered unless absolutely necessary.
(b) An Erlenmeyer flask containing a hot solution is not tightly stoppered to prevent solvent loss during cooling.
(c) The suction of a vacuum filtration apparatus is broken before the vacuum is turned off.
(d) Vacuum filtration is avoided when crystals are isolated from a very volatile solvent.