1.Do these applications runs all the time in the background also when I'm
not connected to WAP or WiFi?
That depends on the specific security application.
2.In case you recommend to have such apps , which applications do you
I prefer being cautious in what I install, rather than having Big Brother Watching Over Me. As a Linux-based system, Android have a very strong security base and the Android framework on top of of it is very paranoid about security. Android is -- for all practical purpose -- impermeable to worm-type virus. However, like any Unix system, Android does not protect you from you taking a gun and shooting your own foot. If you tell Android to trust an application, Android will trust the application; if you give trust to the wrong application, don't blame the system for it.
3.Is it true that the more application I use I can mess up the whole android
system like the registery in ordinary
computers) and it can lead to the
whole device to malfunction or to be
more slow (like ordinary computer)?
If you're installing many applications that starts background services, then yes, it can slow down the system. Applications that are not running does not affect the speed of the system.
4.According to question 3: What can I do to secure my system? Do I have some
option to restore the whole android
system if it will get massed up and
bugy in the future.
There is a bunch.
- There is a factory reset on
Settings > Privacy > Factory data reset.
- If you buy the phone from your carrier, they usually can reflash your phone with original ROM.
- On rooted phones, you can make a Nandroid backup.
- On custom ROMs, you can make a ClockworkMod Recovery backup.
- On many phones you can download and flash 3rd party or leaked original ROMs by yourself.