False.
In fact, they were. The most recent and significant experiments to detect neutrinos include the T2K and SNO (soon to be SNO+) experiments.
Neutrinos are incredibly hard to detect so the "absence" of neutrinos doesn't mean they are not there. It was long thought that neutrinos did not decay. We now know they do so. Thus, the lower than expected number of neutrinos detected coming from the Sun has been fully explained. It took four decades but the problem is now fully resolved.
In a literal sense no, but they have been detected experimentally. The fact that your television works is proof enough that electrons exist, since an electron is required to strike a screen in order to produce an image.
They're predicted in Physics, but they've never been detected yet.
A hypothesis
Hypothesis
Scientific data that has not been experimentally tested is unreliable.
The speed of light is exceeded by several things. Wave guides for instance. However all present theories preclude any information or mass to exceed the speed of light. Neutrinos have never been sent through the CERN collider at super-luminal velocities.
Nobody knows, they have never been detected. For now tachyonic matter is purely a theoretical construct.
Because it had not been experimentally confirmed.
A proposed explaination for an observation is called a hypothesis.
Neutrinos are subatomic particles, which exist in three "flavours" - the electron, muon and tao neutrino (listed in order of increasing ass); each of these also has a respective antiparticle. Most of the neutrinos incident on the Earth are "Solar Neutrinos" (neaning that they are emitted by the sun. The neutrinos oscillate between the different "flavours", which are determined by their respective masses, and are extremely unreactive - more than 50 trillion neutrinos go the human body every second! As the masses of the neutrinos are very minimal - virtually zero - neutrinos travel at near-light speed.There have been several experiments dedicated to the detection of neutrinos, the most notable being T2K and SNO amongst others; SNO is currently being re-activated with enhanced detection prospects through the use of an organic scintillating fluid, as is now named SNO+.