On 1 October 1906, a delegation of Muslim leaders, led by Aga Khan III, met Lord Minto, the Viceroy of India, at Simla and presented a memorandum demanding separate electorates for Muslims in India.
The First Khilafat Conference was held in Delhi on 23 November 1919, to protest against the British policy towards the Ottoman Empire and to express support for the Caliphate.
The improved sentence would be: "Had you been careful, you could have avoided the accident."
This is a conditional sentence, and "had" is the correct auxiliary verb to use in the if-clause (instead of "have" or "had have"). The sentence is expressing a hypothetical situation, and "had you been" is the correct way to form the conditional perfect tense.
The sentence should read: "To his horror, he found that he had slept for nearly 24 hours."
The use of the past perfect tense (had slept) indicates that the action of sleeping started in the past and continued up to the point in the past when he found out how long he had been asleep.