The Dhutangas.
The Sattavisuddhis.
Upadaya-rupas like gender, jivita etc…
Types of causes (hetu, arammana, upanissaya etc.).
Achievable Jhana-levels of the different types of meditations.
What is the Jhana with vicara but no vitakka (mentioned in suttas as “avitakka vicaramattha samadhi”).
Difference between Dhamma-ayatana and Dhamma-arammana.
Difference between Dhamma-dhatu and Dhamma-arammana.
The factors of Mana-ayatana and Dhamma-ayatana.
The factors of The Mano-dhatu, Dhamma-dhatu and Manovinnana-dhatu.
Difference between Mana, Mano-vinnana and Manovinnana-dhatu.
Difference between Mind and Mental factors.
The fact that Apo-dhatu can not be felt by the body.
Paticcasamuppada explanation (in a sensible way).
Nitattha suttas and Neyyatha suttas.
Who appended “evam me sutam” in Suttas.
Why Buddha, Paccekabuddha and Mahasavakas are different in wisdom and the reason for it.
Why no other monk can achieve the level of wisdom of venerable Sariputta.
And many more …