If someone were to ask: Is it permissible for the noun being described to be omitted while the adjective remains?

The answer is: Yes. This occurs very frequently in the Quran and in people’s speech. Allah, Exalted is He, says: “Make full coats of mail, and measure well the links.” [Saba’ 34:11] That is, full coats of mail. And He says: “Except those who believe and do righteous deeds.” [Al-Tin 95:6] That is, righteous actions. There are many similar examples. What is less common, however, is the reverse: omitting the adjective while retaining the noun it describes, because the adjective—the description—is what is intended. Hence Ibn Malik said:

Whatever can be understood of the described noun or its adjective may be omitted;
but omission of the adjective is rare.

His statement, “in the same manner,” means: he performs it as he performed the first rak'ah—that is, with regard to standing, bowing, prostration, sitting, and what is recited in it.

His statement, “except for the opening takbir,” refers to the takbir by which the prayer is begun, for the prayer has already been commenced with it. Indeed, if he were to say the takbir intending it as the opening takbir, his prayer would be invalid, since this would necessarily mean that he had ended the first rak'ah and started the second afresh, which invalidates the prayer.

“Except for the opening takbir and the opening supplication, …”

His statement, “except for the opening takbir,” is necessarily in the accusative case because it is preceded by bi-mā. If it were not preceded by mā, either construction would be permissible: the accusative or the genitive.

His statement, “and the opening supplication”: the opening supplication is likewise not sunnah in the second rak'ah, because the prayer is begun with it after the opening takbir.

If someone were to ask: What if a person were to recite one form of the opening supplication in the first rak'ah and a different form in the second rak'ah?