1. 95@ goes for variable that stores car handle
1.1. Car handle is a memory pointer that stores address of certain variable\structure etc
1.2. This address responsible for car structure
1.3. Structure is a block of variables that responsible for car parameters\variables, i.e. coordinates, health, angle, turn rate etc etc etc
2. No, you can't, if you still can't understand why, it is like if you would put a triangle object into the circle shape, i.e. it wont fit it and boom, crash, apocalypsis
3. Yea it is, quick dive into it : opcodes that have "char" description in it usually affect you, so you use global $PLAYER_CHAR variable, opcodes that have "actor" in it usually affect you and other peds\players (ofc on your side), so you use $PLAYER_ACTOR or PED handle
^ third part may be a bit incorrect in some places, since it is requires way complicated explanation, but I hope you will understand it yourself later