Yes, parts of every underground line on the tube network use stations that are also used by the circular line, and are therefore connected.
The London Underground. Travel For London (TFL) is responsible for the London Underground and the other transport networks in London.
Presumably you mean the London Tube? If so, it is the Jubilee Line (silver).
The track difference of the track layout of the London Underground and London Overground is whereas one is underground the other is over the ground.
Yes, that is correct. You have answered your own question.
Yes, the London Underground S Stock is replacing all the other existing stocks on the Sub Surface Lines.
It's a small passage
The London Underground first opened on 10 January 1863, between Paddington and Farringdon. The railway was then extended, added to and expanded over a period of time. No one person designed the whole of the Underground as a vision.
Generally, no it isn't. However, some individuals might think it is scary, like if they did not like being underground or have some other phobias.
District Line
New York and Moscow and probably many other cities.
There are 11 underground metro systems in the UK, with the London Underground being the most well-known and extensive. Other cities with underground systems include Glasgow, Newcastle, and Liverpool.
That is just a common name that stuck. It is now called London Transport Limited (since 1985) and operates under the name Transport For London. Years ago there were many names for many companies that make up the London Underground. Another common name is "The Tube"