It is recommended you start with lower editions for first starting out. If you buy Pro right away and lose interest in it in only a few weeks, you'd be out a lot of money. With a lower edition, you can at least get started. Many of the features of higher editions can be faked or replicated using alternative methods. Standard may not have terrains, but MDL terrains have more advantages than HMP terrains as it is anyway (freedom of shape, size, positioning, texturing, and, under certain circumstances, even faster). LOD can also be used in standard edition using an alternative method, of which the alternative method is far more flexible than the engine's built-in system with very few disadvantages. By using external edittors, you can get bones mode, but you'd only be able to use vertex animation. For physics, you can write your own physics system. Beams can be faked (to a limited extent) by using some sort of model.