Top tube length on a mountain bike can be measured by using a tape measure. Start from the center of the top of the seat tube (where the seat post comes out) and measure horizontally to the center of the head tube (where the front fork is attached). This measurement will give you the top tube length. Ensure that the bike is level on the ground and the measuring tape is straight for an accurate measurement. This measurement is important as it gives an idea of the distance between the saddle and the handlebars.

To take pedals off a mountain bike, you will need a pedal wrench, which is a specialized tool used for removing pedals. Start by positioning the bike so that the pedal you want to remove is facing upwards. Then, use the wrench to turn the pedal in a counterclockwise direction. If you are having difficulty removing the pedal, you may need to use more force or apply some lubricant to the threads. Repeat the process to remove the other pedal, being careful not to damage the crank arms or threads.

To adjust a mountain bike rear derailleur, start by shifting the bike to the smallest gear in the front and rear. Then, loosen the derailleur cable and adjust it so that it is taut. Next, adjust the high and low limit screws on the derailleur so that the chain is centered on each gear. Finally, fine-tune the shifting by adjusting the barrel adjuster on the derailleur or the shifters. Test ride the bike after adjustments and make further adjustments as necessary.

Yes, you can ride a mountain bike on the road. However, mountain bikes are designed for off-road terrains and may not be as efficient as road bikes on smooth surfaces. Nonetheless, they have sturdy frames and suspension systems that can absorb shocks and vibrations on bumpy roads, making them a great choice for commuting or leisure riding.