Sales contracts are usually what type of contracts? Why?

A agreed to sell B, and B promised to buy from A, A's predator laptop with in the end of the month of September 2021. But, B both C's laptop instead. A is now suing B. B in his defense said that there is no contract. Is B correct? Why?

The following are obligations of a seller.

In the above problem, if B gave 5 pesos as part of the purchase price. What contract was created? Why?

Can you sell something you do not own? Why

A is a retailer in indian mangoes. He buys indian mangoes on wholesale to sell them in retail. A bought from D, 8 kaengs of indian mangoes about 40 kilos each kaeng. Upon A's inspection 3 out of the 8 kaengs has ripe indian mangoes. Can A sue for recission?

Traditio longa manu, Traditio brevi manu, traditio constitum possesorium, execution of a contract are examples of what kind of delivery? Why?

A bought from B jewelry costing 8 million pesos, on the terms of sale or return, sales have a mark up as may be imposed by A. B filed a case for estafa against A. A counters that there is no estafa because there is already a contract of sale. Which between A and B is correct? Why?

A sold his car to X. But A is insolvent. B filed a case of insolvency and included the car A sold to X as part of A's assets. X sold the same car to D, both X and D do not have possession. A public bidding was made and the sheriff sold the car to W. Who owns the car? WHY?