Salam ZKAB90,
First off, that verse you cited says nothing about Allah revealing or granting the knowledge of the unseen or the future to whom He wills; rather it's saying that no one encompasses anything of Allah's Knowledge except [of] what (or whom) He wills.
Secondly, given that no name is given mention to in verse 2:255, then on what conceivable ground can you assert that the phrase save that which He wills [them to attain] is a reference to the prophet Muhammad?
All that said, I have cited you (many of times before) ample explicit verses which makes it abundantly and explicit clear that NO ONE EXCEPT ALLAH knows of the unseen or of the future which have seem to intentionally ignore (I presume because it defeats your whole argument) I'll cite said verses again.....perhaps you'll take understand:
"Verily the knowledge of the Hour is with Allah (alone). It is He Who sends down rain, and He Who knows what is in the wombs. Nor does anyone know what it is that he will earn on the morrow: Nor does anyone know in what land he is to die. Verily with Allah is full knowledge and He is acquainted (with all things)." [Al-Qur'an 31:34]
"They ask thee about the (final) Hour - when will be its appointed time? Say: 'The knowledge thereof is with my Lord (alone): none but He can reveal as to when it will occur. Heavy were its burden through the heavens and the earth. Only, all of a sudden will it come to you.' They ask thee as if thou were eager in search thereof: say: 'The knowledge thereof is with Allah (alone), but most men know not.' " [Al-Qur'an 7:187]
Allah (continuously) says in the quran that the prophet was no more than a human being and had no such knowledge of the last hour. As demonstrated by the following ayats:
"Say, (O Muhammed) "I am no more than a human being like you...." [Quran 18:110]
"Say (O Muhammed), "I am not different from other messengers. I have no idea what will happen to me or to you. I only follow what is revealed to me. I am no more than a profound Warner." [Quran 46:9][/u
"Say (O Muhammed), "I have no power to benefit myself, or harm myself. Only what God wills happen to me. IF I KNEW THE FUTURE, I would have increased my wealth, and no harm would have afflicted me. I am no more than a warner, and a bearer of good news for those who believe." [Quran 7:188 ]
"Say (O Muhammed), "I do not say to you that I possess the treasures of God. Nor do I know the future..." [Quran 6:50]
So the logic from the four ayahs I quoted can be broken down as follows:
Human beings cannot predict any part of the future; prophet Muhammad was a human being; therefore he (Muhammad) could not have foretold the future.
This belief you're clinching to (regrading the prophets supposed prediction of the future/unseen) finds no support from the Quram; in fact, the Quran says the opposite (i.e. Muhammad -pbuh- had absolutely no knowledge of the unseen/future).