what are the other requirement management tools for IBM ? what is the functional differences between all of them?

One answer

You will be looking at Requisite Pro (discontinued), Rational DOORS, Rational Requirement Composer/Rational DOORS Next Generation.
https://www.ibm.com/developerworks/community/blogs/requirementsmanagement/entry/3_reasons_to_throw_away_your_requirements_documents_webcast_follow_up?lang=en
https://jazz.net/library/article/716
https://jazz.net/help-dev/clm/topic/com.ibm.rational.rrm.help.doc/topics/c_differences_doors_dng.html
https://www.ibm.com/developerworks/community/blogs/requirementsmanagement/entry/3_reasons_to_throw_away_your_requirements_documents_webcast_follow_up?lang=en
https://jazz.net/library/article/716
https://jazz.net/help-dev/clm/topic/com.ibm.rational.rrm.help.doc/topics/c_differences_doors_dng.html