To add to what SengKiat stated.
firewns said: “Since sankhara kandha are cetasikas..”
Sankhara are not the same as cetasika, but they are related. Different types of sankhara arise when different combinations of cetasika arise.
For example, if the lobha cetasika (and possibly more related cetasika) arise, then that is an apunna abhisankhara (apunnabhisankhara).
But in another case, dosa cetasika may arise giving rise to another type of apunnabhisankhara.
Regarding the rest of the question:
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1. Vedana and sanna arise with each and every citta. So, yes, they are both in any sankhara.
- Vinnana is the overall sense experience that includes sankhara. Therefore, sankharakkhandha is part of vinnannakkandha.
- But vinnana is more. While vedana, sanna, and sankhara are all nama, and rupa is all rupa, vinnana is the bridge between nama and rupa, leading to namarupa: “vinnana paccaya namarupa“.
- That is a subtle point, so don’t worry too much if anyone does not really understand that yet. For those who need more information: “Viññāna Aggregate“.
- An easy way to see that is on’es own house is a rupa. The name “my house” that comes to our mind comes with a picture that has both the shape and features of the house and one’s feelings, perceptions, desires about it too. So, what comes to the mind is a namarupa.
– That means vedanakkhandha and sannakkhandha are parts of the bigger sankharakkhandha.
– Vedana and sanna are two critical and special types of cetasika. That is why they are listed separately from other 50 cetasika.