1 - It is best to not use any water at all or very little. The entire radiator and connected cooling system should be filled with a good quality coolant. Drain the entire system if it contains water only. Water is bad for the radiator and will cause rust. Other fluids in this car include brake fluid and power steering fluid which should not go below minimum levels indicated on their respective bottles on the top left of the engine bay.
2 - Left side blue cap is for wiper washer.
3 - At 80,000 KM you can take it for a complete checkup Honda 3S dealership which may involve replacing various items (but not limited to the following)
Brake Shoes
Rotor Servicing
A/C Fan Motor inspection Repair/Replacement
Bearings/Hubs inspection
Belts inspection/replacement
All car fluids including coolant, gear oil, engine oil, transmission fluid, power steering fluid.
All types of filters including A/C Filter, Air Filter, Fuel Filter, Oil Filter
CAT inspection, oxygen sensor inspection. You should also get your complete exhaust system cleaned as carbon/MMT deposits build up over time.
Suspension inspection and repair including small suspension parts and shocks/mounts etc
Engine Mount inspection and replacement as needed (engine mount of the reborn is especially weak)
Engine tuning/Tappet adjustments, spark plug replacement
Tyre/Rim check
Hope I did not miss anything 
4 - As mentioned already the Prosmatec transmission in the Reborn is very difficult to replace. You will have to find a compatible CVT transmission from a JDM car which is suitable for the R18A engine and then you can activate the paddle shifters. Manual to prosmatec transmission swap is easier to do.