I bought a 2007 new Honda CRV. What should be the RPM when I accelerate...
 

...the car from a complete stop.? And how will RPM affect the car in terms of mileage and engine... Will it hurt the car if the RPM reaches 4 ??

It doesn't. The RPM basically in simple terms is teling you how much the car strains. Now, there is a more scientific way, but that would take forever to explain. 4,000 is not a high RPM. You can push it up to about 6,500 in this car. Don't be worried. Now if you ALWAYS make the RPM go to 6,500 you will sacrifice fuel economy.