ALL RER stations in Paris are underground, and some in the suburb too. out of Paris, most RER stations are ground level or elevated.
Good grief, no. Only the bit inside metropolitan Paris is underground.
There is and underground section in Paris, but the route of the RER to Versailles is nearly all above ground as regular trains.
Alas, no. What makes it worse is that very few stations have them either. EDIT: the RER trains have toilets. The metro trains don't.
Champigny - Paris RER - was created in 1859.
Auber - Paris RER - was created in 1971.
Joinville-le-Pont - Paris RER - was created in 1859.
Épinay-sur-Seine - Paris RER - was created in 1908.
Underground lines are referred to as numbers or terminus stations which are signposted in other stations to direct the public. The station "la Défense" is on the line 1 ("La défense" to "Château de Vincennes"). There is also a connected RER station (RER is regional railway network, faster than the underground, but having fewer stations) on the same site.
You take the RER A
No, the Paris Metro does not extend as far as the Disneyland resort, but... - there is a shuttle bus from both Paris airports throughout the day to Disneyland, €16 for adults, €13 for children. The timetable and operating hours are available on the Disneyland Paris website. - alternatively, you could catch the RER train link to Paris, and then switch for the RER line A train direct to the resort (Marne-la-Vallée - Chessy). In Paris these RER lines run on the same way than the metro system, but faster with fewer stations.
'le métro' is a network of underground railway stations in Paris and the neighbouring towns. You can go anywhere in Paris with it.
the four-letter display on the trains is a code to help users board the right trains - there are usually several branches and / or terminal stations on each RER line.