Mohammad was not sure about his destination:

Mohammad Wasn't Sure about his destination while all the Bible prophets were surely knew that they were going to heaven after death.

Jabir reported that the Prophet of Islam said: "No good works of yours can ever secure heaven for you, nor can they save you from hell -- not even me, without the grace of God."

Abu Huraira related that when the verse, "Cause thy near relatives to fear," was revealed to the Prophet of Islam, the Prophet arose and began to proclaim: "Oh people of the Quraysh, and you sons of Abdul Manaf, and you Abbas, son of Abdul Muttalib, and you, Safiyyah my aunt, I cannot save you from the punishment of the Day of Resurrection. Take care of yourself, O my daughter Fatimah; you may use my property, but I cannot save you from God. Take care of yourself" (Bukhari).

Abu Huraira reported that the Prophet of Islam said: "No one of you will enter Paradise through his good works." They said: "Not even you, O Apostle of God?" "Not even I," he replied, "unless God cover me with His grace and mercy. Therefore be strong, and morning and evening, nay every moment, try to do good."

Mohmmad's prayer asking forgiveness:

Volume 1, Book 12, Number 711:
Narrated Abu Huraira:
Allah's Apostle used to keep silent between the Takbir and the recitation of Qur'an and that interval of silence used to be a short one. I said to the Prophet "May my parents be sacrificed for you! What do you say in the pause between Takbir and recitation?" The Prophet said, "I say, 'Allahumma, ba'id baini wa baina khatayaya kama ba'adta baina-l-mashriqi wa-l-maghrib. Allahumma, naqqim min khatayaya kama yunaqqa-ththawbu-l-abyadu mina-ddanas. Allahumma, ighsil khatayaya bil-ma'i wa-th-thalji wal-barad (O Allah! Set me apart from my sins (faults) as the East and West are set apart from each other and clean me from sins as a white garment is cleaned of dirt (after thorough washing). O Allah! Wash off my sins with water, snow and hail.)"

is Heven promised in Islam?

Allah Promised hell for his followers:
Al-Imran (The Family of Imran)
Sura 3:185, "Every soul shall have a taste of death: And only on the Day of Judgment shall you be paid your full recompense. Only he who is saved far from the Fire and admitted to the Garden will have attained the object (of Life): For the life of this world is but goods and chattels of deception."

This Suras from Quran very clearly says that after death everyone will go to hell fire then judgment.. When a person went to hell fire then how and why it is possible that he/she can come out from hell fire and go to paradise.. no way.. This verse does not say anything about eternal life. This verse very clearly says that every believer in Allah is tasting death means they did not get the life while Jesus promised eternal life and heaven as we read in

John 10:10 "The thief does not come except to steal, and to kill, and to destroy. I have come that they may have life, and that they may have it more abundantly.

And also every soul is going to hell fire till the day of judgment means they are not reaching heaven. So of course Allah promised hell fire for his believers. I said "no way" for coming out from the hell fire and go to heaven. There is no chance to go to heaven once you go to hell fire... But yes, Jesus can save you when you are still in this world as He said in John 3:15 "that whoever believes in Him should not perish but have eternal life.
John 3:16 "For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.

How a person can save himself/herself from hell fire when he/she is already in hell fire? And this verse says that they will be there till the time of Day of Judgment. Do you think a person who is already in hell fire will get a seat in heaven after judgment? Judgment is a day when people get their sentence and verdict.. no reward my friend that day.

Allah promised hell fire for his followers but contrary to it Jesus promised heaven for His followers.