briandev

Alt-I is also the key bind to take out a radio in LCPDFR. You should change the keys for ELS by opening up ELS.ini with Notepad (or something similar) and changing the key reference number next to each key binding in the Key Bindings section. The reference numbers for each key can be found in the user guide that comes with ELS. If you set keys that do not interfere with any other mods then all of the ELS keys will work perfect.
 
If you mean initiating a traffic stop (while in a police vehicle), you have to use shift. The traffic stop is handled through LCPDFR. Alt-G with Braveheart's Policing Script is used to stop vehicles while on foot for traffic control purposes.
 
Also, welcome!

Welcome to the forums!
 
For the OpenIV issue, you need to replace the two original files rather than add them,  For example, if you want to replace police.wft and police.wtd, right click police.wft in OpeniV and select "replace" and then navigate to the car files you downloaded.  Then do the same for police.wtd.  Also, rebuilding the archive isn't required and sometimes causes problems (from my experience at least).
 
For the big menu, you will need this mod here:  http://www.gta4-mods.com/script/simple-trainer-version-65-f2115