Articles 131 and 132 require violence, the threat of violence, or the use of the victim’s helpless state. Article 131 covers sexual intercourse; Article 132 covers other sexual acts. Their structure and sentences are identical, and which one is charged depends only on what act is alleged.
Article 134 punishes sexual intercourse by a person over eighteen with a person under sixteen, and Article 135 punishes indecent acts with the same age group. Neither requires violence. Neither requires the younger person to have objected. Agreement is irrelevant to liability — it is the age that creates the offence.
That distinction is the single most important thing for a foreign national to understand. A relationship that would be lawful in most of Europe at fifteen is a criminal offence in Russia, and the fact that both people considered it consensual changes the sentence rather than the outcome.