Olympic 

Formation and early years
The name was chosen by James Edmondson, the club's first treasurer, and is believed to have been inspired by the recent excavation of Olympia, site of the ancient Olympic Games. It's referenced by Phythian, p. 7?
Yes, that's right    
Decline and colapse
In 1886 the club's committee was forced to reduce the players' wages to a quarter of what was being offered by Preston North End. Why it is comparing with the PNE? It's because some players went to play there?
Simply because PNE were the top club in the area.  It shows how much worse Olympic's wages were compared to the top club in the area.  Hope that makes sense    
Rivalries
The rivalry became especially fierce in September 1884, when, amid accusations that the clubs were using underhand tactics in attempts to "poach" each others' star players, the Rovers' secretary sent a telegram to his opposite number stating that his club would play no matches against Olympic in the 1884–85 season. It's referenced by Phythian, pp. 63-66?
Yes, that's right    
Cheers!