Note the policy has been extended:​​​​​​ https://www.singaporeair.com/en_UK/d...ary-rebooking/

Make unlimited changes to your booking

With complimentary rebooking, you can:
• make unlimited changes to your booking on or before 31 May 2022; and
• make one additional change after 31 May 2022.

All booking change fees will be waived if your ticket is eligible for complimentary rebooking. All you have to do is pay the fare difference, if any.

Any booking change you make must be before your original travel date or within a year of your ticket’s date of issue, whichever is earlier. For example, if your ticket was issued on 15 June 2021, you must make your changes before 15 June 2022. You can find your ticket’s date of issue in the e-ticket pdf attached to your booking confirmation email.