They are fairly interchangeable, with only subtle differences, at least as I perceive it. But all of the examples are missing either a direct or an indirect object that indicates with WHOM the president will be sharing the information. For example: In two hours, the president will apprise THE PEOPLE of the current situation of the country. In two hours, the president will let THE PEOPLE know about the current situation of the country. In two hours, the president will notify THE PEOPLE of the current situation of the country.

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