Yes.
Any 20inch forks will fit.
The forks go through the head tube and headset, the stem anchors the fork and then the bars attach to the stem, so the answer is the fork and stem.
the fork gyro (if have) and stem and mostly important the headset
It ha a threadless fork with an aheadset stem. Remove compression cap, loosen the steerer tube(rear) screws, pull the stem/ bar off. Then the fork should come off with a light tap on the steerer tube.
That's a BMX, and there's not a lot of difference between forks for those. AS long as you get the correct steerer tube length, any BMx fork would give you a rideable bike.
BMX bikes all have the same size (20") wheels, so they're very similar in size. Doesn't matter that much as they are mainly ridden standing up anyhow.
Depends on what's already on there, what's available, and how much clearance the bike has at the fork and frame.
I think a freestyle bmx should be made out of steel but I've heard bmx's are made out of chromoly or alluminion, i hope that's just for racing
The main parts are: frame fork wheels (handle)bars saddle seat post cranks pedals
Most will fit. but not all. There are a few different designs on bottom brackets for instance, and they aren't interchangeable. If you look at older bikes the stems/fork can differ too.
It's smarter to get a BMX bike instead of a ps3.