is it possible to replace the 2.4 menu with an older one?

Well you need to bring back the Nexuiz/data/menu directory and Nexuiz/data/menu.dat from the 2.3 release.. But why would you want? The old menu was slow and clunky..

is it possbile to use the old nex/nexbeam?

I think the old nex could be used just by getting a pk3 packed of the old model, but I'm imagining that the old nex beam is probably hard coded.

you can get the ladder package which adds a static beam to the existing one from the Rules page of the Nexuiz ladders page.

Or you mess around in and compare the effectinfo.txt files of v2.3 and v2.4 on your own

Those who use the ladder nexbeam have no honor.

yesterday i mixed some 2.3 and 2.4 things n then i had no beam.. Failed.