Good article, but there is not enough information.

How are these done?

"The first one is achieved by a rule called JNtoIdxLookup. The second requirement is a correlated loops join - also known as an Apply. The rule needed to transform our query to that form is AppIdxToApp."

"We can remove this Compute Scalar, and the need to compute COUNT(*), by normalising the GROUP BY using a rule called 'NormalizeGbAgg'."