hi!
Thanks for helping me! Following are the answers for above asked questions,

1, The frequency Range can be from 1Hz to 1Mhz.
2, I think generating a sine wave or converting of sine wave both can be used but I Like the sine wave which will preserve the time period of square wave and also it doesnot have any harmonics. "Think it in this way that if i want to apply pure sine wave to Inductor or Capacitor and then change it frequency until its reactance will become equal to some thing like fixed resistor or other element. And then drive its value from the current output frequency."

Thanks!