Does a person get rewarded for good intentions they did not have beforehand, but are truthful that, had they known about them, they would have intended them before performing the deed?

The apparent (and Allah knows best) is that the reward is commensurate with the intention. Therefore, a person only receives from the reward what they intended from the acts of obedience. However, they are rewarded for their sorrow over what they missed of reward and goodness. They should be keen to bring to mind the intentions of acts of obedience before commencing the action.