They get stuck and clog the pipes.
If you jam a whole head down it and turn it on, yes.
it isn't advised, it will probably clog it up.
Make sure that you knocked out the dishwasher plug on the garbage disposal. If that is already out, then there could be a clog in the line to the dishwasher.
NO. coffee can combine with grease and clog your drain
yes, and if too much, you need a plumber. Also carrots clog too.
Perhaps because they'd probably clog the sink. Think of it, if you put a shell down the disposal and crushed it up, some pieces would most likely not be washed away, leading to bugs infestation, or rotting.
I toss it in the composter. Otherwise, toss it in the garbage, NOT in a sink disposal ! It might clog the unit.
Instead of calling the plumber the next time your garbage disposal clogs, try to fix the problem yourself. First, unplug the garbage disposal. Then, use a broom handle to manually rotate the blades. The broom handle gives you enough leverage to turn the blades even if there is a clog. Once the blades turn freely, remove the material that caused the clog. Only use your hand if you are sure that the power is completely disconnected. Once the clog is removed, plug the disposal back in, press the reset button, and turn it on. The unit should now work properly.
Of course there is no rule against it; however, you do not want to put certain things in your disposal. Potato peels can clog it, for instance. Also, throwing tea bags into your disposal is a bad idea as the strings on the teabags may wrap around the unit's hardware which can affect the performance of the disposal as well as the dishwasher (if it is hooked up with the garbage disposal).
If you have a septic tank or gray water system in your home then do not install a garbage disposal because it has been know to clog up your drain field. If you have city sewer and have a garbage disposal then I would recommend that when using the garbage disposal, you make sure you are running cold water because it helps make vegi's not stick to the sides of your drain and its cheaper and I forget but something to do with spaghetti and disposals don't mix.