Answers to 1, 3, 4, and 5 can all probably be found by searching.

1. This may help: http://www.conitecserver.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=9;t=006562
2. http://dictionary.reference.com/search?q=Assert Not sure if that is what you wanted.
3. Couldn't find any search results that I liked with "portal".
4. Yes, trace(vectorfrom,vectorto) would work very well for this. Look it up in the manual.
5. Look at the templates, they come with a script for bullet holes that spawn when you shoot a wall/floor/anylevelgeometry.

Hope that helps.