Is it acceptable for a scholar to change his fatwas and argue by citing the differing opinions of the imams, taking into account the ease of information availability in the current era compared to the past, which makes choosing the correct fatwa possible from the outset?

What you have imagined is not accurate, and this is from two perspectives: First: A fatwa is influenced by time, place, and surrounding circumstances, so it is inconceivable for two scholars to issue the same fatwa on a specific matter. Scholars have mentioned examples of this, such as the saying of Umar ibn Abd al-Aziz: "New rulings are issued for people according to the new transgressions they commit," and the Prophet's (peace be upon him) prohibition of cutting hands during military campaigns, and Umar ibn al-Khattab's suspension of the Hadd punishment for theft during the Year of Ash. Second: Your statement that a middle schooler can gather the opinions of scholars and schools of thought is an exaggeration; understanding and applying sciences and knowing what is preponderant is not accessible to many people. Changing one's opinion, if it is controlled by legitimate Islamic guidelines, indicates the piety of its holder. The mufti must scrutinize matters, but error remains probable in every human endeavor.