Hey there, I was having the same issue as you, if you look on the very left and right crevices while the seats are folded down you will see two black clips, pop those out with a flat head screwdriver, and you can get the back tops off, then for the back bottom there will be a bolt that the rear upper seats were hiding, take out that bolt and then lift the bottom back seat from the area closest to where the bolt used to be and then it should simply pull off.
The 1991 Honda civic uses 6.5" speakers for both front and rear.
The rear bumper on a Honda Civic is held on using several mounting screws. After remove each screw the bumper will be held on with mounting clips. The bumper can be gently pulled off.
The pump is located underneath the rear seat, to remove it first you must lift the back seat and then remove the cover of the pump that is fastened with 4 bolts
The 2013 Honda Civic has 34.3 in. of rear head room.
The 2004 Honda Civic has 52 in. of rear shoulder room.
The 2014 Honda Civic has 52.2 in. of rear shoulder room.
The 2010 Honda Civic has 52.1 in. of rear shoulder room.
The 2011 Honda Civic has 35.1 in. of rear head room.
The 2003 Honda Civic has 32.8 in. of rear leg room.
The 2005 Honda Civic has 36 in. of rear leg room.
The 2001 Honda Civic has 52.6 in. of rear shoulder room.
The 2013 Honda Civic has 49.0 in. of rear hip room.