Is a Honda CR - V have on demand 4 wheel drive?

ONLY the 4WD models. To check to see if yours is 4WD or 2WD - look under the rear of the vehicle, If you can see a driveshaft coming from the front of the vehicle and operating a differential on the rear axle then you DO have 4WD. If by "on-demand" you mean that YOU can engage it or dis-engage it at YOUR discretion - no. The 4WD engages and disengages automatically as wheel slippage is "sensed" by the transmission and the onboard computer.