Who wrote the following quotes?

There is an Upaniṣadic sayiong that the Brahman is one only, without a second. But the existence of something different than the Brahman refutes this. To this we say: in the mention of “without a second” what does the compound intend? Is it a tatpuruṣa or a bahuvrīhi (attributive compound)? […]

Moreover, which consciousness modifies itself (vivṛt-) in the form of the deployment (prapañca)? To begin with, it is not the notion of [simple objects] like a pot, since the [deployment] is seen also when such notions are not present. And since it is not the case that one can say that if such a notion were not produced, or if it were destroyed, the whole world would not exist. And if one were to say it, [one’s assertion] would be invalidated by one’s sense-perception. […]

If X  appears without Y, even Y appears also without X. For instance, [a cloth] appearing even without a pot [and] a pot itself [appearing] without a cloth.

You have surely understood that we are within a Vedāntic framework (i.e.: using the Upaniṣads as one’s foundamental point of reference, evoking the brahman). What else?

Would you have understood that the framework is not-Advaitin? Probably so, given that the last verse mentioned refutes the sahopalambhaniyama (the rule according to which if two things are simultaneously grasped, like cognitions and external objects —which are only grasped through cognitions— they are not different). However, you might be surprised to know that the author is Yāmuna (in his Āgamaprāmāṇya).

In the light of that, what does the distinctive contribution of Śrī Rāmānuja consists in, apart from systematization and more accurate treatment of many detailed features?

You can read some more open questions on Rāmānuja by clicking on the category “Viśiṣṭādvaita Vedānta”.