Hi gemstar,
A restore will entirely replace the included entities - plugins/themes/database/etc. - so, if the virus infection was in one of those, then yes, restoring will get rid of it.
You will also want to unzip a new copy of WordPress core from http://wordpress.org/download/, as the virus might be in there. (Or alternatively for convenience use UpdraftPlus Premium, which backs up WordPress core too).
Where can I see a UpdraftPlus Backup restore guide
Is it a trick question? :-) 1. Go to google.com. 2) Type in "updraftplus restore guide"
Is it possible to do a new full backup daily, instead of incremental backup?
All backups are full backups. A future release should add incremental backups as an option, but it's not ready yet.
Best wishes,
David