Hello @drqamu.
It is good to see you back in Steemit Crypto Academy. Your explanations are really good and You have explained every topic in simple words which makes it easy to understand.

Short selling is not possible in the spot market, but it is achievable in leverage trading (futures/margin/options).

Correct. We cannot short sell in spot market but In Leverage trading, We can short sell which is a plus point of leverage trading.

Good luck for the contest.