Hi, there is an online User Guide available, here's the link, http://dl-www.sonyericsson.com/cws/download/1/102/323/5/1314105076/ST18i__UG_EN_1252_5370_1.pdf
You are able to view running apps by the following steps, goto Settings>Applications>Running services. However, it is best not to touch them, let the Android OS manages them.
If you are worried about your mobile data, goto Settings>Wireless & networks>Mobile networks, untick Data enabled (when not required).
