The Qur'an is always described by God Himself as plain and manifest. Let me remind you that a Bedouin Arab might come to the Prophet and sit with him for an hour or so, when the Prophet would have explained to him the basics of Islam. The Bedouin would then declare that he is a Muslim and might go to his people and explain to them his new faith. Many of them would respond to his call and adopt Islam. That might have represented all their Islamic education, and they would nevertheless be good Muslims and through conscientious following of the principles of Islam secure for themselves admittance into heaven.
Asceticism calls for severe abstinence and austerity.
An ascetic person is one who practices severe self-discipline, and may retire into solitude for this purpose. This is also against Islam, because Islam wants its advocates to mix with people and call on them to correct their behavior and adopt what is certain to earn God's pleasure.