Does Allah forgive polytheism upon repentance from it, and what is the manner of repenting from polytheism? Is there a specific supplication for that?

Shirk (associating partners with Allah) is the greatest of sins, and Allah does not forgive it for those who do not repent from it. Therefore, repentance from all its types, major and minor, is obligatory. Allah accepts sincere repentance, which involves abandoning shirk, submitting to Allah alone, regretting what has passed, and resolving not to return to it. Islam nullifies what came before it, and the door to repentance remains open as long as the servant has not reached the gurgling (death rattle) stage. Whoever falls into major shirk must offer sincere repentance, rectify their actions and intentions, and it is legislated for them to perform ghusl (ritual bath). Minor shirk is more subtle, and it is warded off by saying: "O Allah, I seek refuge in You from associating anything with You knowingly, and I seek Your forgiveness for what I do not know."