hello ace users

i recently bought this phone for rm980 (standard package = 2gb sd, charger, n so on)

at first the phone seems okay but..............

1st prob
today i don't know why the ram is almost at its max..i tried to clear the memory in the task manager but it frees only a little..then i delete some apps but still the same thing..at last i shut down the phone and wait for a while and turn it on again..thank god the ram consume lesser than before..what could cause this prob? is it the monitoring apps? or is it something else?

2nd prob
is anti virus apps is necessary for android? (im new to android)

3rd prob
when i first got the phone i log into the google account and download some apps..i dont know why the phone keeps asking me for password in the notification area..how to disable this? i have disable the pocket data and background data..

4th prob
i cannot get my swype function worked out? how to configure it?

5th prob
i know rooting void the warranty but is possible to unroot after u have root the phone? if im not mistaken, there is an unroot function on SOC 1.7 right?

this is my first android phone and i really want to get the best out of it

thx divine