The only way as the crow flies (through space and explodes) to get to the Alpha Quadrant from the Delta Quadrant is to arrive at the centre of the Galaxy, then find the absolute centre of whatever that "place" is, and then stand on the geometric axis of the galaxy, which even then would superposition you simultaneously in the Alpha, Beta, Delta and Gamma Guardrants... So baring cheating with wormholes and the suchlike, you gotta go through the Beta Quadrant (or the Gamma Quadrant) to find the Federation in the Alpha Quadrant.
1.The centre of the Galaxy is a mess of black holes every thing else revolves around which would be a bitch to navigate through even without a manchild at the helm.
2. The Great Barrier (Star Trek Movie 5.) is unpassable. Sybok did something funky that opened the door, but other than that, unpassable.
3. I'm being a dick. Sorry.