What is the ruling on plucking a hair out of forgetfulness, or a wife kissing her husband with the intention of apologizing, or prostrating on an insect by mistake, while in the state of ihram for Umrah, and what are the consequences of that two weeks after returning from Umrah?

Removing a nose hair while in the state of Ihram necessitates a fidyah (expiation) according to some scholars. As for kissing one's wife without desire, there is no harm in it and no fidyah is required for it. Regarding killing a fly during prostration, no fidyah is due from you according to the majority of scholars, because flies are not considered game (sayd) for which Allah Almighty has mandated compensation.