It’s been almost a decade, but there are pretty reasonable public transport options around the island or they have an Uber like service now call Grab. Looks pretty cheaply priced.
Everything should be doable within a day since I seem to recall having done everything.
Unique (like most universal not a ton): but Mummy is the best iteration. Jurassic Park they utilize a raft instead of a flume. Madagascar Crate Adventure (if still open) is one of your more unique offerings - but unfortunately it’s not very good.
There are some recent offerings like Puss in Boots (a simple coaster) and Spaghetti Chase (a simple dark ride) that will be unique.
Then BattleStar Galactica is probably the main standout.
It’s all very well packaged and looks very nice, but I think the main reason you hear of Limited Westerners going to Singapore for USS is that it really lacks anything groundbreakingly different. Formerly it was the first to open Transformers and I had never actually been on Spider-Man at the time. It’s the McDonalds of theme parks.
Singapore is a nice place to visit though!