Hello and first of all welcome to my guide, I will definitely help you how to get to 100% discovery.
There are pictures to see how you can do it.
The red-marked color are for Hidden Roads.
Western District
There are only 2 Hidden Roads far.
Central District
There are 0 Hidden roads far.
Wan Chai
There are 0 Hidden Roads far.
Causeway Bay
There is 1 Hidden Road far.
Quarry Bay
There is 1 Hidden road far.
Chai Wan
There are 2 Hidden Roads far.
Shek O
There are 28 Hidden Roads far.
Tai Tam
There are 24 Hidden Roads far.
Stanley
There are 8 Hidden Roads far.
Happy Valley
There are 10 Hidden Roads far.
Aberdeen
There are 17 Hidden roads far.
Victoria Peak
There are 9 Hidden roads far.
Pok Fu Lam
There are 6 Hidden roads far.
Repulse Bay
There are 4 Hidden roads far.
