How do i edit a action replay cheat on r4?

How do i edit the usrcheat file to put more cheats on the r4?

Use R4CCE etc.

Download the newest cheat database from cheats.gbatemp.net. No need for editing.If cheats for a specific game don't work, get r4cce, open the "usrcheat.dat", and search for the correct game on the list that appears. If you clicked on the name of the cheat-folder, you press the "..." button and search your ROM. Save, and, TADAH! Your cheat works for that one game now!

How often do they update cheats? Do I have to redownload everytime they update ^.^

Yes (only if you want the cheats that they add of course). Which is why you view the changelog.

Redownload as soon as they have cheats for a ROM you want, they update often, but redownloading is only needed if you want cheats for a specific, newly added game^^

Can i put two ore more cheats on two games?