Over a decade after his first, Rachmaninoff conducts the second symphony himself in 1908. It was received well, and got him the Glinka prize (his second). Rachmaninoff must have felt a lot better. To me, the symphony sounds more lyrical, has more melody than the first one.
This work has been the subject of a lot of revisions, mostly by Rachmaninoff himself. It was just too long, over an hour. The revisions cut the length down to 40 minutes, but are usually no longer performed or recorded. This one is a version with a minor cut, but not complete.
About being complete: the manuscript was on permanent loan to the British Library until 2014, when it was auctioned. It is not on public display since. I understand it has some stuff in there that is not in any of the published versions. Says wiki. Does that include new music, or is this about notes from the composer? Both might be interesting.
The third part, the adagio contains probably the most famous melody Rachmaninoff has written, I’m sure even non classicists wil recognise it.