Will God forgive insults that resulted from provocation by neighbors, and will repentance be accepted without having to deal with abusive neighbors or ask for their forgiveness, given that they have offended more than once indirectly?

Repentance from reviling people unjustly requires seeking their pardon and forgiveness. A poor relationship does not nullify the obligation to seek forgiveness, unless the reviling was in retribution or reciprocity, in which case the right is forfeited. It is stated in the Hadith (definition) that "Whatever the two reviling parties say, it is upon the initiator, as long as the wronged person does not transgress." Reviling a Muslim unjustly is forbidden, and the one who has been reviled is not permitted to retaliate except in kind, as long as it is not a lie or a slander.