No. You can't visit the garden if you are not a traveler.

The airside area is a gazetted secure zone, so you are not legally permitted to just hang around and use it as a rest point and are expected to move to immigration . Its permitted to grab something from a shop, have a bit of a look around but there are limits of reasonableness if you are not using the hotel rooms or other paid facilities. Police do do sweeps (though they do this most at night as the main purpose is stop people using the airside area as a free hotel) and will remove people without onward boarding passes [I've seen them doing it]. There comes a point where the carousel with bags is moved to the next flight and then your bags go to lost and found and you have to claim them. This is no longer a nice secure room at the edge of the baggage hall but is now a relatively open area by the carousels. Staff do still watch them and you have to identify the bags to retrieve them as they are cabled down. Once past immigration, you can do what you like - the Jewel particularly is set up just for this. That said, any decent hotel will have a luggage room and let you leave bags there and get outside for the day. Better ones will have shower access so you can freshen up and change before going out, or the airport has such facilities for a fee. So that is an alternative and at the right time your room might be ready (though at the 9:30-10am-ish we are talking that obviously has no guarantee in a popular spot.

It is free to access before immigration. With regards to the baggage, it may be left at the ‘Left Baggage’ area. Maybe can check with the staff withh regards to it.

Yes - if you have time, you can go between the terminals easily using foot/train.

The interconnecting tram comes every 5 minutes or so and it only takes a couple of minutes between terminals. So quick and efficient. We got home to Australia and realised that T1 I think has a huge slide 😩 so upset we missed that one lol would definitely have taken the kids on that 🤣

the airport is so user friendly. The Butterfly farm is clearly signed. Google it and you will see the opening times. It is free, not very big but worth seeing.

You'll want to collect your checked in baggage before going to all these attractions. All are at the passenger transit area, so save your immigration formalities for last. Ask any airport staff for directions. They're very helpful. Alternatively you can still visit some of these sights upon leaving Singapore. Just get to the airport early.

Hi there, enjoy your time at Changi, one of the worlds great airports. Yes, after check in to see the attractions, each terminal has a information booth to find out what is on for that terminal. Plus there is a train that will take you between the terminals, so make sure you try to catch them all if you have the time.

Мы были в саду бабочек днем. Насчет ночного посещения я точно не знаю но мне кажется нет. Сад находится под куполом с прозрачной крышей для проникновения естественного освещения. А ночью его фактически нет. Если честно то на режим работы не обратила внимания. Днем было хорошо. Красивые бабочки и приятный сад с тропической зеленью. А это всегда хорошо в жаркий день.

Not sure but presume because it's in the departure hall that it's open all the time.