The CVT or in the case of any AT in any car made today will not let you do anything outside of the normal operating range. So yes you can put the car in MT mode it will pick the closest manual gear ratio for your current speed and then you must use the paddle shifters to change the gear ratios.
Keep in mind that when the CVT is in Automatic mode you can still use the shift paddles and the CVT will hold the manually selected gear you have shifted to till it picks up a change in throttle input then it will go back to full automatic mode.
Example while in Automatic mode you can down shift say to 3rd gear while going down a long hill to keep your speed checked - after you have hit the bottom and given the car some gas to keep your speed going the AT will drop back into D mode by its self.
If you selected Manual mode the car will stay in 3rd gear till you either put it into Automatic mode or you change the gear using the paddle shifters.
The only time I use manual mode is when I'm off roading and need to hold a specific gear, towing my boat up the boat ramp again need to hold a specific gear, Or while driving up a very long steep climb where I want the car just to hold one gear and not change it every time the throttle input changes slightly or the road incline changes a little etc.
When preparing to pass very rare case where I might need to get a jump to pass I will go to manual mode drop the car to say 3rd gear to get the engine wound up a bit - then when I can pass the engine is already putting down power and ready to jump. However even when left in Automatic mode which is 99.9% of the time the CVT will easily get the car powered up and moving plenty fast in most cases.
I have to say the question made me smile. I realize what a knucklehead I am. I just started banging on the paddles and gear shifter as I was driving the car home from the dealership. Had to see "what happens when..." while driving home. Nice to know some people are more careful.
I've found it easier just to keep it in Drive and, when you need a little goose, just hit the left paddle. The computer won't let you drop it to a blow-your-engine gear while in motion. You just hit the desired level of gear, do what you've got to do, and then the car resumes Drive once the speed and RPM's level out. No need to use the shifter at all.
Ok not related to the Op's question but this is the perfect thread to ask. Sometimes I use the paddles when driving two-lane winding canyon type roads, it takes an otherwise boring car and makes the drive feel somewhat more enthusiastic. Also the car is always in the Powerband when you come out of tight corner or off an apex.
I also occationally use the paddle shifters when say I want a jump or rabbit-like start off the line. Our CVT is horrible at starting from a dead stop when you want max or near Max power from the 2.5. The Pre selected 1st gear point appears to be lower than whatever the CVT chooses for you and what I find when you up shift to 2nd using the paddles in this situation is almost like getting a sling-shot like boost, at least in my car. I only use this feature rarely but when I do I greatly appreciate them. I would hate to be left with just the CVT only.
My question though is..... Is it bad or hard on the CVT transmission if you stay On the gas while you up shift the car or should or do you guys let off in between up shifts? My car seems to up-shift lightning fast almost like rapid fire and at times I wonder if that's to harsh for the CVT? I also try to blip the throttle as to rev- match when ever possible, it's tricky with how fast the car changes the gear points when downshifting coupled with a somewhat slow to respond drive by wire throttle but fun when executed on a twisty back road.