Here's your answers, or at least states what I will personally
do...
1: The video has some weird sound on C651, is this a train
problem (Need improvement) or video problem (Known as lag a bit
PC)
Probably train.dat, but engine/motor sounds are to me the
hardest part to do for the train.
2: How do you guys know the speed limit for each track
sector?
Guesswork and GPS devices?
3: How do you guys know CGA is a cross and not like one in Choa
Chu Kang / Pasir Ris
Same way you found out Choa Chu Kang is a V shaped crossover -
look out of the window?
4: The C651 seemed to me left the triangle hand grip on top.
Explain further? I don't get what you mean...
5: In (Open)BVE, is it possible to create a Changi Airport -
Pasir Ris direct train (It need a reverse in Tanah Merah)
A "mock" one. Basically you have to select Jump to Station, then
CHANGE ENDS or something like that, but that, be more exact,
is a "non-standard" way, which creates another station
simulating the "CHANGE ENDS" functionality further down the
road - a "unintended" use of the track.sta and track.station
commands.