I did not know (Shifting)

Yes, you can make tranny shift under power in most bikes. That is NOT how you SHOULD do it however. You should use the clutch, just a quick hit is plenty. It is MUCH easier on the tranny than slamming the gears together under full power. Most trannies are pretty durable so they will take quite a bit of ABUSE but will eventually fail. Shift forks can be bent and gears can wear excessively, even break teeth off. You can imagine what follows a tooth breaking off in the tranny. Unless I was in the front of the pack and there was good money on the line I prefer to use the clutch. I have to pay to fix my stuff.

i hardly ever use the clutch on my bike.
but i do take the gas off befor i shift and just say it may not want to shift i would use the clutch but that have only happed once that i can remember.