I was thinking, most condo/service apartment units are normally stick side by side with each other, with only 1 layer of wall apart won't you be able to hear what your neighbour is saying or what they are saying?

Also side question,

Is the fire escape normally lock or open at all times? Cause if it is open at all times, what is the purpose of those lift security and if it is closed, won't it be dangerous if there is emergency?

Normal landed linked house , their walls also stick side by side... so it's the same thing

The only difference is you could hear noises that transmit through solid floor from above. E.g. dragging furniture, real heavy footsteps, jumping etc..

Usually the fire escape is just the stairs which should be open all the time

If it is open all the time, what's the point of the security then? Most serviced apartment only limits you to access your own floor with your given card. If the emergency stairs is open at all time, what's stopping me from going to another floor whenever I want?

can access from any level but to go out, only door at lobby accessible

Means 1 way entrance

Fire door at emergency stair cannot be locked, just closed.

For some condo, the firedoor is not accessible from outside, but can be opened easily from the inside via a button or various close door mechanism.
So no problem from for escaping while outsider cannot access simply, thus no problem for security reason.

For noise, normally main noise come from upstair dragging furniture, kids jumping up and down.
Next door noise seldom can be heard, except if the apartment indeed uses extreme thin and porous brick to build the wall, or heavy sound like large KTV set.

If the wall is using red clay brick, generally won't much an issue for next door noise.