How do I Cite relevant cases and legislation only for these:

James has 2 ads

The first ad says the watch can withstand anything or your money back. Three weeks after seeing the advertisement, someone's watch becomes filled with water and it didn't work. They asked James for a refund and he didn't accept.

The next one is a television commercial with a voice over that says, "For every friend you refer to buy a watch, you can earn $10.00 cash on us!" The commercial shows images of a young man speaking to friends as a bank balance flashes on screen with higher and higher amounts up to $100,000.00. Natalie manages to refer 120,000 people to purchase watches through her Instagram page and seeks to claim the full cash amount. James refuses.

How do I advise Kate and Natalie of their rights using relevant case contract law?

Also:

A guy decides he wants to encourage a girl to stop playing video games. That guy offered to give the girl a car if he "stops spending too much of his time playing on his Xbox over the next month". They signed a contract with the exact language used.

Girl stopped playing video games for three weeks. Guy tells girl that the car is actually a vintage Mustang worth a significant amount of money and in great condition.

One week later, Karim seeks to enforce the contract for his Mustang. Mustafa reveals that the car is actually a 1996 Toyota Corolla worth about $700. Karim demands a Mustang under the contract.

How do I advise Mustafa for the other one?