Sure there is current before 0,7V! As you see in the equation the built-in voltage depends on doping (and temperature) so you can play with it to some extent by controlling the doping. Not to mention that electron-hole recombination is a statistic phenomenon and therefore when you say 0,7V it does't mean that there is no current at all at lower voltages.
As for the depletion region, it can not be significantly reduced or disappear. It exists there because you put two differently (p and n type) doped semoconductors together. And yes, it can be extended when you reverse bias the junction
You can take a look here to find a well written and more descriptive approach:http://hyperphysics.phy-astr.gsu.edu/hbase/solids/semcn.html