1. There are a few about, some are purely landscape, others are more travel. The one that immediately springs to mind in the UK is Take a View: Landscape Photographer of the Year. While it was tarnished this year due to an apparent inability to ensure that people follow the clear rules of entry, it still remains the highest profile one I'm aware of. It is open to photographers worldwide, but the photograph must be taken in the UK. It has the added advantage if you are looking for some exposure of publishing a book with all the commended entries, with web address of the photographer.
2. You have to read the rules carefully with any competitions and then make a judgement. Some competitions (thankfully they now seem to be in the minority) state that copyright of all images is transferred or they have full commercial licencing rights, allowing them to make money out of any of the photographs without any recompense. Most of the high profile ones state that they will use images to promote the competition only. Many of these high profile ones (such as Take a View) also publish a book, with the potential of publicity for the photographers. Anyone entering has to decide whethet the potential gains are worth accepting the rules for.