Yes, the clutch can wear out just like a cars. However on our 25 hp bikes it will take quite a long time. Just like in a car; clutch life is determined by how you drive. I went through 3 clutches in my rx7 in a matter of 2 years...but I did burnout's all the time and had around 400 hp. Since you cant drop the clutch to do a burnout (unless you want to wheelie onto your back..), the clutch should last a lonng time.
Shifting without the clutch wont do any damage to the transmission, however I HIGHLY recommend NOT downshifting without the clutch. The sudden shock on the drivedrain under decel could cause the rear tire to lock up momentarily, possibly causing some bike droppage. A high speed 6-5 shift is probably ok, but lower gears like 3-2 and DEF. 2-1 will cause the tire to skid.