Take the S shuttle train (color code grey) west across 42nd Street, from Grand Central (East 42nd) to Times Square (West 42nd).
At the Times Square Station, transfer to the Downtown 1-2-3 trains (the red line). You could also take the Downtown A-C-E (the blue line) but this will require you to walk an extra block west underground (the A-C-E runs up and down 8th Avenue, while the Times Square Station is at 7th Avenue. So there is a tunnel connecting the A-C-E to the Times Square Station, so you can transfer without exiting the subway system). It's easier to just take the 1-2-3.
Take the Downtown 1-2-3 or A-C-E ONE STOP, from Times Square (West 42nd) to Penn Station (West 34th).
VIA subway
Not possible these days. Amtrak no longer has service to Grand Central Terminal. BTW - Grand Central Station is the subway station. The railroad station is Grand Central Terminal.
Grand Central Station
Grand Central Terminal is the name of the railroad station at 42nd St/Park Avenue. Grand Central Station is the name of the subway station which is below Grand Central Terminal.
Yes- Grand Central Station is the name of the SUBWAY station which is below ground (4, 5, 6, 7 and "s" 42nd St Shuttle lines). The RAILROAD station (MetroNorth Railroad) is known as Grand Central Terminal and is at street level.
To get to 26 Federal Plaza from Yonkers using the subway, first take the Metro-North Railroad from Yonkers station to Grand Central Terminal. From Grand Central, transfer to the 4, 5, or 6 subway line downtown. Exit at the Brooklyn Bridge-City Hall station, and from there, it's a short walk to 26 Federal Plaza. Alternatively, you can take the 2 or 3 subway lines from Grand Central to Chambers Street, which is also close by.
No, they are two separate subway stations.
No, but it does stop at penn station and you can take the subway
According to Wikipedia and the MTA themselves, 77 of New York City's subway stations have working bathrooms, and 28 of these stations are in Manhattan. However, according to the Related Link (see below), in Manhattan, only 8 of these stations are actually functioning and open to the public (9 including "the developer-financed wonder bathroom at the Times Square Station"). The only one on the 6 line is the Brooklyn Bridge-City Hall Station. There are also bathrooms at Grand Central Terminal, downstairs, near the food court. The 4-5-6 line stops at 42nd Street-Grand Central Station, but Grand Central Station is the subway station, while Grand Central Terminal is the railroad station. So, you would have to exit the subway system to use the bathroom, and then pay another fare to get back on the subway.
Grand Central Station & Terminal are located at East 42nd Street between Park and Lexington Avenues. Grand Central Station is the subway station, where you can catch the 4-5-6 (the dark green line, aka the Lexington Avenue Line) or the S shuttle train to Times Square. Grand Central Terminal is the railroad terminal, for trains that are not part of the New York City subway system (like MetroNorth commuter trains).
Atlantic Terminal in downtown Brooklyn. The Atlantic Terminal on the corner of Flatbush and Atlantic connects the Long Island Railroad (LIRR) with most of the Brooklyn and Manahattan subway lines. Grand Central and Penn Station in Manhattan have more tourists, but Atlantic Terminal in Brooklyn has more locals.
MetroNorth from Poughkeepsie goes to Grand Central. Amtrak from Poughkeepsie goes to Penn STation. It's very easy to take MetroNOrth to Grand Central and then get the subway to Penn Station.