Congratulations on your new boat. You picked a winner.
I have not found any information of that detail written on the R25SC.
If this is your first time splash don’t forget the hull drain plug. It is located on the starboard side aft where the bottom of the hull meets the keel.
As far as seacocks go, on the R25SC it does not have the traditional seacock. It has a thru hull with a ball valve attached. These ball valves are closed when the handle is 90 degrees to the valve body and open when the handle is parallel to the valve body. The main ball valve to open for engine operation is under the engine hatch on the starboard side. The valve feeds a large sea strainer which supplies sea water to the engine, head, and raw water wash down. Depending on your boat equipment configuration, you may have 2 other ball valves, one for A/C and one for the generator. Both of these valves are located on the port side under the engine hatch. These do not need to be in the open position unless you are going to operate that equipment.
One other valve to open prior to starting the engine is the fuel valve. It is also a ball valve and is located under the step as you enter the cabin. On my boat I have a black access pannel on the face of the lower step. Opening the pannel will allow you access to the valve which is on the top of the fuel tank. If you have a generator there will be 2 valves on the top of the fuel tank.
If you have a Volvo Penta engine there are 2 other valves under the engine hatch. These valves are for providing engine coolant for the hot water heater and the cabin heater. These valves can be either in the open or closed position for basic boat operation. They are also ball valves and are located near the oil dip stick and the back of the engine. If you have a Yanmar engine I am not familiar with that configuration.
What I have stated above is the standard factory configuration for a 2014 R25SC, I assume your 2012 is probably the same. Also, if the prior owner has made modifications to the boat the configuration may differ.
I hope this helps.