Answer:
1. The Mongols could not extend their empire into northern Africa. - The Mamluks defeated the Mongols.
The Mamluks were a class of slave soldiers who proliferated in the Arab World during the Middle Ages, especially in Egypt. Mamluks from Egypt and the Levant defeated the Mongols at the Battle of Ain Jalut, in Galilee, modern day Israel.
2. The Islamic culture of the captured states influenced the Mongol rulers to convert to Islam. - By 1256, the Mongols established the Ilkhanate, which was made up of mostly Islamic states.
The regions that made up the Ilkhanate are most of Anatolia (modern day Turkey), Persia (modern day Iran), most of the Caucausus, Northern Iraq, and Southwestern Afghanistan and Pakistan. The vast majority of people in these areas have been muslims since the arab expansion of the Early Middle Ages.
3. Russia lagged behind western Europe in development. - The Mongols failed to improve conditions in the Golden Horde Khanate.
The Golden Horde Khanate comprised a territory that stretches from modern day Kazakhstan to Ukraine. This area remained poor during the Mongol rule.