Hello everyone… I need to use 2.4 ghz xbee 900 hp for waspmote sensor. Is it possible to use that version with waspmote?
The term “900” in “XBee 900HP” represent its frequency. So there can be no XBee 900HP operating at frequency other than 900MHz. 
But if I understood motive of your question correct, you can look at “XBee Pro S2C Programmable” modules. It as same micro-controller that 900HP uses and it operates on 2.4GHz frequency. But it operates on a different communication protocol known as “Zigbee” (which is a standard protocol btw).
Ok thanks There is smth else that i wanna know. Can i put a custom CSMA/CA mac code on that programmable version?
I don’t think you can do that. CSMA/CA needs to be handled at radio level (not MCU) and Digi do not share source code of radio’s firmware in public.
Asgen is correct. In addition, Ember which is who’s process Digi is using for the Zigbee mesh enabled product does not allow you to control the RF side of things.