From Sinai?

1. If you were convinced that the concepts of the afterlife, the resurrection of the dead, the days of the Messiah, reward and punishment, are not speculations of the sages, but are actually transmitted from Sinai or they know it with the Holy Spirit, would you believe in it (like Maimonides, etc.)?
2. If not, why not?
3. If so, what should be the convincing evidence that it does indeed come from Sinai?
4. Why is this different from the many laws and interpretations that did not clearly state that it was from Sinai but we accept them only because we are convinced that it was? (39 Maalach for example.)