no it does not lose air in a plane it just has a hole in it or it has high or low pressure
I think you are allowed knitting needles in your luggage that goes into the plane hold (main luggage), but you are not allowed them in your hand luggage because they can be classed as dangerous. If you want to knit on the plane, I have used pens before. If you use some thin pens or pencils, that should work.
Yes, you can breathe in a luggage compartment. Also the compartment is pressurized. However, you would be freezing cold, because it's not climate controlled.
Checked luggage is that which has been checked in: weighed, labelled, and taken away to be loaded onto the plane. You don't see it again until you have landed at the other end and the plane is unloaded. Hand luggage is that which you can take onto the plane with you and have access to during the flight.
Plane-side is a derivative of gate-check in terms of luggage. Plane-side luggage is generally used to describe luggage that was gate-checked, but left on a designated cart next to the stairs of a small aircraft. This cart of luggage is then taken and loaded into the cargo hold of the aircraft. Upon arrival, the luggage is taken off first and carted to the aircraft stairs for passengers to retrieve.
You can't put it on carry-on luggage, but you can put it in the luggage that goes under the plane
NO
No.
the pressure is high out side the plane because the air moves around quickly.
yes
As long as your infant has a plane ticket, their luggage is aloud. However, for certain items you may have to consalt the plane board, or someone at the airport.
Provided they do not exceed the cabinet weight and size limit, in theory yes, speakers can be taken on a plane in hand luggage.
you can