How does EndowUs Cash Smart ensure the interest rate is maintained at a certain level? Will there any potential loss of value if we put our money in?

For the second part, Endowus Cash Smart invests in money market funds. These funds invests in short-term debt instruments, and they pay out earnings in the form of a dividend. The objective of these funds is stability and keeping the net asset value; not losing your investment. While it is possible to lose money like all investments, the risk is low.