1) Yes the Qur’an is clear in stating 3 main times for salat. Sunnis don’t accept because when you follow a school thought and consider others wrong you get blinded to the truth. Sunnis don’t follow the Fiqh of Ahlulbayt. They follow others who were not infallible (like Abu Hanifa and others). Hence they go it wrong. Historically that had more political power and more numbers so they think they are correct.
2) Just reading Qur’an and acting pious does not ensure guidance. Yazeed read Qur’an too and Iblis worshipped God for thousands of years. One must be 100% open to the truth and humble the heart to the truth. Many Sunni scholars have stubbornness in them and they don’t want to give up their path. Their love for some companions blinds them. The Prophet (s) never said hold on to the companions, he said hold on to the Ahlulbayt. Maybe you have done something sincere in your life and Allah found it worthy and so He gave you hidaya. Make sure you work hard everyday for your faith so you don’t lose it.
3- When you don’t follow Ahlulbayt you go astray because:
-You won’t be worshipping God true way he wants
-You won’t be praying like the Prophet did
-You won’t understand the Qur’an properly
-You end up having false beliefs
-You follow the opinions of fallible people like companions and leaders of schools of thought
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