2.1 branch vs. 2.9 branch

[Ronald Crummett]

Hi - 

Just a couple of general questions regarding the two dominant branches 
of Octave:

1.  What are some of the main differences/advantages between the 2.1 
branch and the 2.9 branch?

2.  I do recall reading, once, that many of the Octave-Forge functions 
have been incorporated into the 2.9 branch - but not all, right?  So if 
I install a 2.9.x version I would still need to install Octave-Forge - 
but would doing so override some of the functions included in Octave?