apache hadoop versions 2.0 vs. 0.23

Question

There are so many Hadoop versions and different distributions which make me confused. I have a few questions.

1. Apache Hadoop 1.x is from 0.20.205?
2. Apache H

Answer 1

According to this blogpost from Cloudera:

There is next to no functional difference between 0.20.205 and 1.0. This is just a renumbering.

Hadoop's Yarn site states:

MapReduce has undergone a complete overhaul in hadoop-0.23 and we now have, what we call, MapReduce 2.0 (MRv2) or YARN

It's also worth to have a look at this diagram too. It shows the tree of different Hadoop versions as well as the 3rd party distributions on top of them.