I have never done the Free tour , but I have done the MLE layover a bunch of times and it usually goes like this:
Arrival at SIN early am.
Go to SKL for shower and breakfast.
After breakfast , I go to the T2 Left luggage located before clearing immigration. (Flight to MLE leaves from T2 , so it is easier when returning later in the afternoon).
Clear immigration and customs , ( You still fill out an entry and departure form).
Take train into the city and walk around , explore and or shop If i need anything or just check out all the stores .

I know my way around Singapore , so I do quite a bit of walking around
just to wake up and try to adjust to the time.
After I had enough , or like last summer when It started pouring out.
I go back to airport, collect my stuff and hang out at the SKL until boarding time.
You will get dinner on the SIN-MLE flight , but I have never been awake to see it , I usually eat at the SKL and pass out as soon as we take off.