Which films in the series does this series follow?

The first 4 seasons were filmed in different trailer parks in Nova Scotia, Canada. The pilot was filmed in Spryfield, Nova Scotia. The first season was filmed in Sackville, the second in Dartmouth, the third in Lakeside, the fourth in Dartmouth again (in a different park than the second). For the Christmas special and season 5 and onward, they have used a park they purchased in Dartmouth.

In several episodes, there has been talk of a "Mushroom War", meaning the mushroom cloud of a nuclear missile has been seen by people living in the Land of Ooo. Marceline is a vampire that is 1,000+ years old, yet she was shown as a child in the ruins of a city when the Mushroom War had stopped. Ice King is also 1,000+ years old, as it has been shown that he was a human before the Mushroom War. If you pause at the beginning of the introduction, you can see a cassette and an old tv - both from the 80's. As well as this, there are nuclear bombs which haven't yet exploded. This probably means that the Great Mushroom War took place in the 80's. Therefore, Adventure time is probably around 1000+ years into the future

It takes place from 2364-2370 A.D. 95 years after the events of the original TV series, 94 years after the events of the animated series, & 71 years after the events of the Undiscovered Country movie.

It is an adaptation of a series of British books written in the late 1980s. The author is a former British political figure. If anything, it (and the BBC series which followed) is based on British political figures.

Yes, it was adapted into a series of live-action films in 2006.

It is considered significant because of several occurences in the series. Dekalog: One, Two, Four, Six, Seven, Eight and Nine.

Unlike American television, where even premium-cable series typically have at least 10 episodes, British television has many recurring series that have only a handful of episodes. Highly regarded shows such as "Foyle's War" and "Luther," for example, have only two to four episodes a year. More than that, the people behind "Sherlock" treat their work as something different from simply making extra-long television programs. In an August, 2011 press release from BBC One, "Sherlock" co-creator Steven Moffat responded to suggestions that there should be more than three episodes in each season/series by saying, "We think of them as films because they are ninety minutes long and once we knew we weren't doing hour long episodes they needed to be on that sort of scale. They have to have the size and weight of a movie."

David Chase has said that he wanted to make a film. But he cannot find a way to properly do the series justice. So until/unless he finds a way; the answer is no. With many of the major characters not surviving the final season and the recent untimely death of James Gandolfini, it can be assumed a film will never happen now.