Is the prayer of one who made a mistake in some of its postures, such as vocalizing where one should be silent, or made a mistake in pronouncing some words, while ignorant of that and unintentionally, valid and sufficient for him, or must he repeat it, and is expiation required for that?

The prayer is not invalidated by reciting aloud in a place where silence is prescribed, or vice-versa. However, it is sunnah (definition) (recommended) to observe each in its proper place. According to the Maliki school, prostration of forgetfulness (sujud (definition) as-sahw) is performed for both cases. If the error in prayer relates to the Fatihah, the opening takbir (takbirat al-ihram (definition)), or the obligatory portion of the tashahhud (definition), in a way that changes the meaning, and the worshipper was able to correct it, then he must make up the prayers he performed with this error, because a Muslim is obligated to learn the rulings of prayer.