Does Fatwa No. 38987 mean that the doctrine of the Righteous Salaf accepts multiplicity or does not deny multiplicity, unlike the Ash'aris who deny duality or multiplicity?

It is impermissible for the Sunnis to sanction multiplicity for Allah Almighty, and whoever believes that is a disbeliever. The intent of the fatwa is that whoever directs worship to other than Allah is a polytheist, even if he believes that Allah alone is the Creator and Sustainer of the universe. For the belief that Allah alone is the Creator does not benefit unless the servant directs all his acts of worship to Allah alone, contrary to what the words of some theologians suggest, that monotheism is the belief that Allah alone is the Creator. Polytheism is the worship of other than Allah, even if the polytheist acknowledges that he is a creature. It is not meant that the Ash'aris permit the worship of other than Allah, but rather that some theologians restrict the meaning of monotheism to what has been mentioned and do not clarify what contradicts it, namely polytheism.

As for language: one can begin grammar with Al-Ajurrumiyyah with a simple explanation, and rhetoric with Al-Balaghah Al-Wadihah, along with abundant reading of literary works.