Who was the dog in marley and me?
No context provided
Which dog plays Marley in Marley and Me?
22 different dogs
No context provided
Which dog plays Marley the most as an adult in Marley and Me?
Clyde
Marley & Me (film)
https://en.wikipedia.org/wiki/Marley%20%26%20Me%20%28film%29
Marley & Me is a 2008 American comedy-drama film directed by David Frankel from a screenplay by Scott Frank and Don Roos, based on the 2005 memoir of the same name by John Grogan. The film stars Owen Wilson and Jennifer Aniston as the owners of Marley, a Labrador retriever. 
Marley & Me (film)
Because the film covers 14 years in the life of the dog, 22 different yellow labradors played the part of Marley (as revealed in the special feature Finding Marley on the DVD).
Marley & Me (film)
Marley & Me is a 2008 American comedy-drama film based on the 2005 memoir of the same name by John Grogan. The film stars Owen Wilson and Jennifer Aniston as the owners of Marley, a Labrador retriever. Because the film covers 14 years in the life of the dog, 22 different yellow Labradors played the part of Marley. A Labrador named Clyde, plays Marley the most as an adult. 