I remember during cpf life debate in parliament, WP did asked the minister whether cpf life could go bankrupt and the reply is YES.
That's correct. It's
possible for the Government of Singapore to go bankrupt. Not very likely at all, but technically possible. Planet Earth can go bankrupt if it has an appointment with a big enough space rock. "So what?"
If tomorrow someone invented a pill could extend life expectancy to 120 years, I will expect a responsible government to cut cpf life payout by at least half. If the government do nothing, I will withdrawn my OA and SA and convert them to other currency or gold.
In that hypothetical you'll be very happy indeed that you're getting a monthly income for life, which now lasts to about age 120, when you are that much more likely to outlive your savings. As it happens you probably won't be allowed to skip CPF LIFE, so why not make the most of it?
Is it possible for SA to hit ERS before the age 55 if a person bulk transfer a lot OA to SA and also top-up a lot cash to SA during his/her 20s and 30s?
Yes, absolutely. Hypothetically a generous person could deposit $192,000 (the entire 2022 Full Retirement Sum) today into a Singaporean citizen newborn's Special Account. That money will grow at >4% interest (thanks to some bonus interest), and that growth is faster than the growth in the ERS -- or at least it seems to be. So eventually the ERS will be reached and crossed.
That's an extreme example, but with compulsory contributions still streaming in over a working career it's very possible for a worker to hit the ERS in his/her SA well before age 55. OA to SA transfers and cash top ups are at least quite helpful, but also helpful are the Additional MediSave Contribution Scheme (AMCS) and minimizing MediSave withdrawals -- buying the public hospital Integrated Shield plan instead of the private hospital one, for example. That's because at some point MA reaches the Basic Healthcare Sum, and contributions and interest on a "full" MA then flow into SA until it reaches the Full Retirement Sum. So a "full" MA drives up the SA faster to the FRS. Past the FRS it's only the compulsory contributions and interest that continue adding funds to SA.