I found there are 2 types of online courses available for cadence tools. One is ILS (interactive learning series) and another is "Virtuoso Online Training Course Collection".
Can you please explain what is the difference between two ?
The best thing is to use the "Contact" link at the bottom of the Virtuoso Online Training Course Collection link that you sent. Asking here, which is a forum for issues with the forums themselves, not for technical or sales questions is not going to get you an answer.
As far as I know, the collection is a package to allow flexible access to multiple ILS training courses; an ILS training course is just for a specific class.