This movie was made with one purpose: to trick people into buying the DVD/blue-ray of "Jack the giant killer", only to be disappointed it isn't the blockbuster movie "Jack the giant slayer" they thought it was. There cannot have been any other reason or intention for making it because this movie is the very worst of utter crap. It really is just the stolen movie title filled with garbage. However, there is a story in there. It has actors, it has special effects, though extremely bad, appalling, awful. The movie has inconsistency written all over it. Nothing makes any sense, at all. The script, the acting, props, action scenes, - nothing measures up to any standard other than making a buck from stealing the title from a blockbuster by just throwing something together badly without much of a budget. The dinosaur cgi was half decent though. I cannot blame the actors for bad acting, when probably everything was shot in one take. There simply may have been no time or budget to re-do anything. Perhaps the actors were also lured into this sham, ignorant of it's true nature. There should be laws against this shameless deceit. On the other hand, some bad movies - because they were done badly, either for the lack of skill or on purpose - gain a cult status. This one will not.
Just to describe some major issues: Jack, an ordinary kid, is building/finishing some sort of battle robot as in "Avatar". The feet of the thing are shown several times walking on grass, in the opening scene. Clearly, it is just a couple of cardboard boxes with some spray paint. And he's building this thing for what reason? And with what means? No matter, he's got it working right in the nick of time, to kill the giant dinosaur in the end scene. Another delight is the flying castle. The "engine room" is nothing but an old smith's forge with forging tools hanging on the wall. The beans don't add up. Jack receives two beans. Which he throws away into a field (and grow into a beanstalk). Later, his stepsister finds another bean in Jack's jacket, and plants that one. At the very end of the movie, Jack manages to find another one of those beans in his pocket. Even if he threw away only one bean and inconsistently put the other in his pocket, still one extra bean has magically appeared somehow.
As mentioned in the other reviews, the time setting is inconsistent - old cameras and modern helicopters. Well the list is really endless. My conclusion is, that if you have ocd and enjoy counting goof-ups, you might like this movie a lot. Also it might be fun, to try to explain all the apparent inconsistencies.