Are the upanishads later to the Vedas?

Question

This question is in connection with my previous question related to Puranas and upanishads. It is also a follow up to my another question.

Chhāndogya Upanishad verses 7.1.2 and 7.1.4 mention the Itihasa and Puranas as the 5th Veda.

It also mentions about Lord Krishna the son of devakI.

Another verse from brihadaranyaka mentions vedas and upanishads itihasa etc separately. Which shows vedas were already arranged into upanishad brahmanas etc.

Here is the BrihadaranyAkopanishad's verse that mentions the four Vedas and Upanishads separately:

The King Janaka asks YajnavAlkya "KA prajnata yAjnavalkya|" OR "What is PrajnA, YajnavAlkya?"

To that YajnavAlkya replies:

VAgeva samrariti hovAchA | VAchA vai samrAr vandhuh prajnAyatarigvedo yajurvedha sAmavedah atharvangirasa itihAsah purAnam vidyA upanishadshlokAh sutrAnya anuvyAkhyAnAni ... vAgvai samrAt param brahmam ||

BrihadAranyakopanishat 4.1.2

The meaning is:

O king, the vAk is the prajnA. By VAk a firend can be known. By VAk the Rig Veda, the Yajur Veda, the SAma Veda and the Atharva Veda, the ItihAsas, the PurAnas, the VidyAs, the Upanishads, the Shlokas, Sutras, the explanations of them and the supplementary explanations (anu vyAkhyAni) .. etc can be understood. That VAk is the Param Brahman.

From the Upanishad's 4th adhyAya's 1st BrAhmana (called the ShadAchArya).

Since I discussed in this question about classification of the Vedas into four, people came up with references which show that the Vedas were classified into FOUR somewhere towards the end of dwapara yuga.

People came up with reasoning that the Purana and itihasa mentioned in the chandogya are actually not the texts like mahabharata, ramayana, and puranas written by Vyasa but it talks of events that happened in the past. Even if that is accepted, we still get a major question here.

Were the upanishads written when the vedas were already classified into FOUR during the end of dwapara yuga?

If not then how come it talks of the fifth veda?

Can it be concluded that the major upanishads (as chandogya is one of the oldest upanishads) were written around the era of veda vyasa ?

PS: Some people believe that everything repeats in every kalpa. However, they come into existence only when the event actually occurs in that particular yuga. Else the text should mention if it talks about prophesies of upcoming yugas.

Answer 1

Even Upanishads are to be considered part of Vedas(eternal). Perpetually all four Vedas co-exist, and because the yajur-mantras are the most prominent, the complete corpus can be called Yajur Veda by the hermeneutic rule, adhikyena vyapadesha bhavanti ("A name may be assigned according to the most prominent category of a mixed group.").

Before Shrila Veda-vyasa's editing, there was only one undivided Veda which actually means the four different kinds of mantras comprising the four basic Vedas were then mixed together indiscriminately, along with other explanatory and historical texts. Intelligent people before Kali-yuga were competent enough to locate the particular mantras they needed from the unordered collection. Only for the generally corrupt age of Kali is it necessary to divide the Vedas into separate parts. The Bhagavatam's analogy to explain this process is that of a rich man's collection of rare jewels. An owner of many diamonds, rubies, emeralds and sapphires who has been keeping them mixed in one box might have someone sort them out for him into four separate piles. After this has been done, nothing has changed substantially in the collection, only the order.

rig-atharva-yajuh-samnam/ rashir uddhritya vargashah catasrah samhitash cakre/ mantrair mani-gana iva

"Shrila Vyasadeva separated the mantras of the Rig, Atharva, Yajur and Sama Vedas into four divisions, just as one sorts out a mixed collection of jewels into piles. Thus he composed four distinct Vedic literatures" [Bhag. 12.6.50].

Which means the terminology of 4 Vedas is not invented at the end of Dwarpar yuga. Hence, there is no fault, if itihasas and puranas are referred in Upanishads as 5th Veda eternally.