What is the Sharia guideline for those from whom knowledge is acquired, in light of the proliferation of social media, and how can one verify the uprightness, piety, knowledge, and God-fearingness of speakers on these platforms?

Speaking about the religion of Allah is a serious matter, and knowledge should only be acquired from those whose competence has been established. Indeed, Ibn Sirin said: "Verily, this knowledge is your religion, so be careful from whom you take your religion." You can identify those qualified to issue fatwas by referring to Fatwa no. 124726.