RedsYWNA is correct. MF Global failed, and its account holders recovered fully 100% of their assets at fair market value. This information is easy to find and a matter of historical fact.
Banks in Singapore back(ed) many things, including Hyflux's bonds.
Correct. When DBS Vickers shut down its remisier (offline retail) business last year (2019), it shifted those clients to UOB Kay Hian. When Schwab shut down its retail business in Singapore, it gave account holders advance warning and asked them to move to another brokerage of their choosing before a deadline. Interactive Brokers and TD Ameritrade were common alternatives (as some people in this forum with Schwab Singapore accounts reported), and Firstrade was/is another possibility. Schwab waived all their transfer out charges. Some U.S. persons were able to transfer to Schwab U.S. if they wished. If/when the deadline passed without an account holder taking action, I believe Schwab closed the account and sent the proceeds to the account holder. I doubt that actually happened much, though, since everyone got plenty of warning through multiple channels and didn't have to pay Schwab any fees.
OptionsXpress and E*Trade also had affiliates in Singapore and closed up shop. OptionsXpress was acquired by Schwab, and for some time after the acquisition OptionsXpress kept its own platform. Eventually OptionsXpress account holders became Schwab account holders with the Schwab platform, and Schwab retired the OptionsXpress brand. E*Trade followed the same course as Schwab in pulling out of Singapore.