What is the difference between RTOP, MTOP, and MCP?
MCP is maximum power that can be used indefinitely without shortening the life of the engine.  You might use MCP when you need all the available power during single engine cruise, to maintain an altitude for obstacle clearance, or when climbing single engine.
MTOP is normal maximum for takeoff and initial climb, with a time limit. If you exceed the time limit, you will shorten the life of the engine.
RTOP is a power reserve for special situations, like when an engine quits, where the engine goes above MTOP to save your butt.  When that happens on modern turboprops the dead engine will autofeather and the live one will automatically go into RTOP (sometimes called &quot;power uptrim&quot; or something similar).  If it does so it may have an impact on engine life or may require a special inspection later.