Well really if you got the game pre-ordered , the game comes with the Professor Genki Uniform and other weapons / cars that he uses.
Do all of the professor Genki's mission thingys
Depends. There is one Genki event in the regular version of Saints Row 3, Professor Genki's Super Ethical Reality Climax. There is also a Genki DLC with many more themed events, this is bought seperately.
you just answered your own question right.
Yes. Even if you kill him, he can reappear.
You get the 'mascot' type homies.
Genki can only be found randomly, there's no way to make him spawn, no specific area he's more likely to appear in, etc.
10
Download the genki girl DLC pack and get guns and new vehicles.
It is just a rumour, it does not exist.
If you mean 'Professor Genki's Super-Ethical Reality Climax' activities, then you just walk over to their icon and start them in the usual way. If you mean the DLC pack Genkibowl VII, each activity is played out in turn as you proceed through the DLC's missions.
If it is installed, check your missions for 'Apocalypse Genki'.
It was a pre-order... with the man cannon... It may become DLC