2 Why don't all communication devices function off the same wavelength?

Wavelength is the distance between identical points in the adjacent cycles of a waveform signal propagated in space or along a wire. In wireless systems, this length is usually specified in meters, centimeters, or millimeters.

Wavelengths are an important factor in Wi-Fi networks. Wi-Fi operates at five frequencies, all in the gigahertz range: 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz and 5.9 GHz. Higher frequencies have shorter wavelengths, and signals with shorter wavelengths have more trouble penetrating obstacles like walls and floors.

As a result, wireless access points that operate at higher frequencies with shorter wavelengths, often consume more power to transmit data at similar speeds and distances achieved by devices that operate at lower frequencies, with longer wavelengths.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me