So here it goes.
Does the plastic surface (Where the friction stickers is put on) of the Duncan Freehand Zero is Sufficient (As what the video says it above) to make a 3mm groove on it?
How to remove FHZ caps? the one the you’ll gonna smash the axle on the ground? or not? 
The FHZ when you buy it, there is a free spacer and a bearing right? 
Yes, the walls are thick enough to make the groove.
When removing the caps, you could use the cap slam method, but it’s easier to just take something sharp, get it under the cap and then pr it out. If that doesn’t work out for you, then use the cap slam technique.
When he says slam he means it. You don’t just push the axle through or you will break the cap. If you slam it, it will pop right out.
If you decide to pry it out you will have a mark where you dug the tool in.
Either way works though. I just slam em. I do at least 40 or so a year and haven’t broke one yet.
When you get a FHZ, I don’t think you get a free bearing. Spacers are a standard when you purchase a Duncan(unless the yo-yo doesn’t even use a spacer).
I’m sorry I forgot about that part of the question.
Yes when you buy an Duncan that uses FHZ type spacers then you get an extra pair free with it. Its their way to widen the gap.
High walls also Pheenix even Glitter/Sparkle/Clear FHZ?