No, Darugis won't be catchable. Darugis is the final boss battle in the game. He's not even a pokemon so he can't be caught. He's just a gathering of all the negative energy in the world manifested into the 3 pokemon who's power it absorbed the most.
Beta 2 won't be the final one. Beta 2 will be concluded after you obtain the 8 badges of the first region & have an epic climax-like battle with a particular pokemon's shadow form. After the battle, the beta will end but that is not the end of the game because Darugis isn't defeated yet. So the cast travels to the next region called the "Omni" Region. I orginally planed to spilt it up into 2 hacks. But Tajaros gave me the idea to put it all in 1 hack because it'll be less work & overall just better. In That region, it'll have 8 gyms (The 8th gym leader being the champion of both regions) & tons of more events. It'll feel as if you're playing 2 hacks in 1. That's the goal...