I like very much what you are doing here. I agree largely with what Michael B. says, and will add the following:
In the eighth measure after the Un poco meno mosso
indication, I would like to hear more of the counter melody in the alto, particularly I would like to hear it move right through to the G in the next measure and then continue F#, G, A - very hard to do, I know.
On the last page, particularly starting at measure 72, the "melody" - if we can call it that - seems to get a little lost in the sixteenth-note chords that follow. I know that the score is marked ff
[/b] at this point, but I do think that the melody should continue to be the main focus, and not the repeated chords.
I particularly like your tempo for the opening section. You don't rush it and, for the most part, you keep it fairly steady which is much to your credit. I also like your tempo for the middle section but - and here it's just a matter of personal taste - I would linger a little more on the two note phrases at the end of measures 36 and 38 (F#, A): note the tenuto
mark on the F# each time. Later where that idea is repeated in a three-note phrase (measures 43 and 45: F# G, A), I would also "linger" a fraction on the F#. This is Rachmaninov and this lush writing can be milked for all it's worth, I think. Again, that's just a personal thought; you may not agree.
Apart from your skipping two measures in the middle section, this Prelude certainly seems to be competition ready. Very well done! Congratulations!