Geologist Yegor Yeniseyev, resident of St. Petersburg

Geologist Yegor Yeniseyev, resident of St. Petersburg, May 10, 2003. went along with the geological expedition to Eastern Siberia. From that moment on, his relationship with his parents, who lived in Vyborg, was interrupted.
On May 15, Yeniseyev´s parents got into a car accident and died on the spot. After their death, there remained a brick four-room house with a land plot in the town of Vyborg, recorded in the name of his father Yegor Yeniseyev. On May 25, the brother of the deceased, Igor Yeniseyev, who also lived in Vyborg, applied to the notary´s office with a statement about accepting the inheritance. On November 16, he was issued a certificate of inheritance.
On November 25, Igor Yeniseyev sold the house he inherited with all the property he owned and the land plot to Antonina Aleshina, and put the received money on a term deposit in Sberbank of the Russian Federation.
On November 30, Yegor Yeniseyev returned from a geological expedition to St. Petersburg and immediately left for Vyborg to visit his parents. There he learned from Antonina Aleshina about their death and about the sale of the house by Igor Yeniseyev. The latter, on the request of Yegor Yeniseyev for the extradition of the money received for selling the parents´ house, refused, saying that he acted according to the law, believing that Yegor Yeniseyev did not want to accept the inheritance.
Is it possible to assume that Igor Yeniseyev had the right to inherit his brother´s property in connection with the non-acceptance of the inheritance by his brother´s son?
What actions should Yegor Yeniseyev take to extend the deadline for accepting the estate of the deceased father?
Can we be considered valid reasons for missing the deadline for accepting the inheritance of the deceased father by his son?
In which case it will be possible to accuse the notary of improper performance of their duties in connection with the failure to inform Yegor Yeniseyev about the inheritance that has been opened?
On what part of the inheritance is Yegor Yeniseyev entitled to rely on and in what expression should it be given to him?
Can a court invalidate a certificate of inheritance rights issued earlier by Igor Yeniseyev? And if state registration of his right to a house has already been carried out?