Is a person held accountable for actions they commit while unaware whether they are permissible (halal) or forbidden (haram)? And does enjoining good and forbidding evil become an individual obligation (fard ayn) if one believes there is no one else to undertake it?

A Muslim must acquire religious knowledge to ask scholars about what is unclear to him. Ignorance of a prohibition lifts the sin if the matter is obscure, such as for a new convert to Islam or someone raised in a country where knowledge is scarce. However, for someone who has lived among Muslims in a country where knowledge is widespread and who had the opportunity to learn, yet committed a sin whose prohibition is well-known, his claim of ignorance is not accepted due to his negligence in learning. Forbidding evil is a communal obligation (fard kifaya), and it is not waived by not being a scholar as long as one is confident in the sanctity of what he is condemning.