What is the way to sincere repentance and returning to Allah after committing sins, claiming knowledge of the unseen, lying, and falsely swearing by the Quran?

The door of repentance is open and will not be closed in anyone's face, no matter how great their sin, until the sun rises from the west. What you have mentioned regarding sins does not constitute apostasy from the religion. However, you must repent from all of them with a sincere repentance that fulfills its conditions, which are: abandoning the sin, resolving not to return to it, and regretting having committed it. You must also return any money you took from people unjustly, without informing them of it.