Singapore airport layover of 24 hours

If you get Singapore visa before hand, below are the options that can be done:
We walk around Clark quay, art gallery marina bays sands , gardens by the bay , Marina bay sands mall at night - mainly lighting at night for 3 to four hours . Don't enter any

Next morning we did universal studios and sea aquarium at Sentosa island

Morning options - sea aquarium, universal studios, jurong bird park , art gallery if you interested. 

Evening options - Marina bays sands, gardens by the bay ( lightings are good in general and go upto to midnight )

In case you plan to be at airport :

Singapore Airport is also one of the best airports in the world. It is the only destination where you can clear immigration 48 hours prior to your flight deprature so you can enjoy all there is in Singapore. Here are a few things to keep in mind at the airport with a strategy in terms of timing:

1) Clear immigration at Singapore

2) Proceed to the Jewel, it is at the Airport, but will require a skytrain to get there. 

3) Start off at the Walking Net. Tickets are 18.90 and 13.90 for adult/child respectively. It should be a "fun" walk. Or, you could go to the Bouncing Net, which is 24.90/19.90 respectively. Both are open till 10pm at Canopy Park (Level 5)

4) A HSBC Rain Vortext Light and Sound Show (requires crossing immigration at the Singapore Jewel at the Airport). It is the world's tallest indoor waterfall and there will be a lgiht show at 10.30pm for free which should not be missed

5) Take a walk around the Shiseido Forest Valley, open 24 hours

6) Proceed through Singapore Immigration and take a train to Terminal 1

7) Head to the Cactus Garden, a rooftop garden highlighting more than 100 species of Cacti

8) Head back to Terminal 3 (your flight will leave from T3, in 99% of the situations), and proceed to the Butterfly Garden, a 24 hour garden with over 1000 tropical butterflies

9) Relax in the lounge before headed to your flight.

As an FYI, if you ever find lounge food quite limiting (in Singapore options for vegetarians are limited) there will always be a 24 hours food court. Just ask any of the lounge staff and I"m sure they will guide you as necessary.

Keep in mind, lounge acess is for you and +1 guest. The second guest will be chargeable

2) As an Indian Citizen, with a Canadian PR, you are allowed to enter Singapore for up to 96 hours. If you choose to do so, I have added a Singapore Arrival Card. 

3) You will have access to three lounges during your stay. I have information online to suggest that lounge access will be limited to ~3 hours for Priority Pass lounges, so with the three lounges, you should be well taken care of. I would recommend the following strategy:

1) Marhaba Lounge from 9pm to 12mn (they close at 12mn) [After Passport Control, find the escalator on the right - between Louis Vuitton and DFS. Proceed up to Level 3, and the lounge is located opposite Singapore Food Street]

2) Ambassador Transit Lounge (12mn to 2.30am) [Departure Transit Hall, Level 3. Located at the east/north end of Terminal 3 next to the Butterfly Garden. Access via escalator or lift located near the B gate corridors, and next to Wines and Spirits by DFS. Located close to the Ambassador Transit Hotel]

3) SATS Premier Lounge (2.30am to 5.30am) [After Immigration Control, turn left. Take the escalator beside Shilla Cosmetics Duty Free up to the lounge entrance on Level 3.].

The SATS Premier Lounge is the best of the three lounges, hence I recommend using them the last.