NO. Some of the energy consumed by a heater is converted into visible spectrum light and some into noise. I am speaking of just the heating elements of course. The equation gets even worse if the fan and control system are taken into account.
No heat is IR not visible spectrum. Noise, in this case, is vibration, which is coupled into the air, if there is any.
The real reason nothing can be 100% efficient is entropy.
No.
First off technically heat is just the energy in matter above that when it is at absolute zero. When it is coupled into the surrounding environment it does so in the Infrared portion of the electromagnetic spectrum. "Light" as the term is commonly used refers to the visible portion of the spectrum, i.e. that portion which the human eye responds to. So no light is not heat.
Yes vibration can produce heat but it does not need to, it depends on the medium through which it passes. In a vaccum an object can vibrate all it likes but nothing will happen.
I would suggest you go study thermodynamics and heat transfer for awhile.
Try a book. You'll learn more.
Then all I can suggest is you stay away from difficult topics, like reality.