Basic manipulations with lists

Suppose I have a list of the following form:

List={{{a,b,c},{d,e,f},{g,h,i}},{{j,k,l},{m,n,o},{p,q,r}}}

I have two questions:

A) How can I convert this to a list of the following form:

Newlist={{a,b,c},{d,e,f},{g,h,i},{j,k,l},{m,n,o},{p,q,r}}

B) How can I access, say, the elements a,d,g,j,m,p?

This is probably a very basic question but I do not have previous experience with Mathematica.

Thank you,