That valve is the 'emergency tanks charging valve'. It is used to charge your emergency air tanks in case they are empty. Now I believe this is only used on the ground by the ground personel but looking at this picture you can see that it connects the main air tanks to the emergency air tanks so in theory you could use the pressure in your main air tanks to pressurize the emergency pneumatic system. I'm not sure tho that the main air supply has enough pressure to do this.
Canopy jettison is the red handle above the ejection handle which you push forward to jettison the canopy and then pull the ejection handle to eject.
The plane has two hydraulic systems which are 'utility hydraulic system'(gauge located between the emergency valves for you flaps and gear) and 'lateral control hydraulics system'(gauge located in front of your throttle). Utility hydraulic system is the one controlling your flaps, gear and air brakes. Now in case you lose your utility hydraulics you can extend your gear and flaps with the emergency pneumatic system(pressure gauges located in front of the emergency valves). Both your gear and flaps have separate air tanks.
Here are the steps to operate flaps/landing gear if your utility hydraulics fail. (Note that this is my way of doing this and these steps are made by my understanding how the system works.
1. Rotate the 'emergency control valves' for your flaps and gears fully open. This pressurizes the system.
2. Lower your flap and gear handles fully to the extended position.
3. Pull the 'emergency gear handles'. (I believe this releases the hydraulic locks connected to the extension cylinders.)
Notes:
- First check that your emergency pneumatic systems have pressure. If they don't, open the emergency tanks charging valve. If this doesn't work prepare for a belly landing. :joystick:
- Everything I said including the guide is based on what I have read from here and here.