By "lasted version" I guess you mean the latest (most recent) version 5.3.6?

You can't check files for malware before download.
The latest versions of LW will cancel a download if the file is deemed 'dangerous'... for example if the file info doesn't match file format. Click on the link below for more info:
http://www.gnutellaforums.com/348490-post9.html

LW does not have a built in virus scanner. It's still up to the user to make sure that they use a good AV program. Keep it updated & use it to scan all files that you download, before you open the file. Click on the link below for more info:
http://www.gnutellaforums.com/350144-post2.html

No, you can't set LW up to avoid malware.
As above, LW will cancel some files before download is finished.
But it's your responsibility to scan downloaded files before opening them

Try it & see... everyone has different apps that they prefer. From my point of view LW's easy to use. Ease of setup depends a bit on your system. Read the User Guide & FAQ, or the sticky threads in different forum sections here.
Frequently Asked Questions - LimeWire
LW 5 FAQ - LimeWire
User Guide - LimeWire

You can set LW's options so that you won't be able to download copyrighted files. In LW Tools > Options > Search. Tick the box 'Don't allow me to download or upload files copyright owners request not to be shared' > ok (click ok to save any changes within Options).

If this is your first time using LW then you should read the FAQ & User Guide before getting started.