Hi,
application what you need occasinaly install to SD card. Minimum application on memmory save the energy. 2G-3G. In first view it's speed .2G uses GPRS/EDGE maximum (teoreticaly) about 100 kbit/s. 2G uses standard frequenncy of GMS network. 3G have theoreticaly limits up 20Mbit/s (this is know as HSPDA, UMTS technology). 3G uses different frequency, different technical aspect.