Minecraft wiki entry for Development, associated text: Respawning when pressing R worked just like in 0.0.13a_03 and prior, as this was not changed until the public release of 0.0.14a.
The mouse features (auto breaking/building when left-click is held down, scroll-wheel block picking support and pick-block with middle mouse button) were all added on May 27, 2009 for the full release of 0.0.14a.