Here is the full list of all 30 Jet Set Radio achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Unlock Garam and use him as a player character
Complete a level without collecting a Recovery Spray Can
Make 100 civilians jump out of your way
Fall more than 20 meters off a building
Unlock Gum and Tab
Start the game for the first time
Complete the tuorial
Complete Chapter 1
Complete Chapter 2
Complete Chapter 3
Create your own graffiti in all sizes
Complete every level with a Jet rating in all game modes
Collect all Graffiti Souls
Unlock all characters
Destroy all helicopters in a level
Perform a 100+ trick combo
Shove the two civilians in No. 540 level before the choppers show up
Finish the game without anyone latching onto you
Tag at least one rival gang member within 30 seconds
Complete all missions with any rating
Draw graffiti 5 times on Onishima's back
Perform a Turn Trick in game
Unlock Poison Jam and use him as a player character
Unlock non-masked Poison Jam and use him as a player character
Unlock Noise Tank and use him as a player character
Unlock Love Shockers and use her as a player character
Unlock Pots and use him as a player character
Unlock Goji and use him as a player character
Use all graffiti in missions
Unlock all songs in the bonus menu