Is the withdrawal symptoms usually the opposite of the effects and side effects of the drug

Yes, true. Withdrawal occurs because your brain works like a spring when it comes to addiction. Drugs and alcohol are brain depressants that push down the spring. They suppress your brain's production of neurotransmitters like noradrenaline. When you stop using drugs or alcohol it's like taking the weight off the spring, and your brain rebounds by producing a surge of adrenaline that causes withdrawal symptoms.

The freezing point of the ice is lowered because of the rock salt which then allows the ice to observe heat from the ice cream mixture without it melting.