Does Allah forgive all sins through repentance, and do the many expiations that cannot be fully paid fall away from one's responsibility, or do they remain and count as misdeeds on the Day of Resurrection?

Whoever repents with a sincere repentance that fulfills its conditions, Allah will erase the sin from him, no matter how great it was, even shirk. And all sins, if a servant repents from them, Allah will accept his repentance, as Allah Almighty says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'"

As for expiations (kaffarat), they must be performed if the sin is one for which expiation is obligatory. Some of them are waived due to inability, such as the expiation for intercourse during the daytime in Ramadan according to some scholars, and the expiation for intercourse with a menstruating woman according to the Hanbalis. Some are waived by death, such as the expiation for Dhihar according to the Hanafis and Malikis. Some expiations remain a debt (in the person's responsibility) and are not waived by inability; rather, they must be performed when one becomes able, such as the expiation for breaking an oath. So, if one remains unable until death, it should be paid from his inheritance. If he has no inheritance, then his matter is left to Allah Almighty. One must hasten to perform the expiations that are affordable and bequeath them to be paid from the inheritance upon death.