What happen to our funds if the roboadvisor close down during bad recession and our invested value are at an all time low, will all the funds be sold or we still hold on to the ETF/funds invested?

The roboadvisor uses algorithms plus human decision making.

In times of crises the companies should stick to certain rules, but are free to let the roboadvisor work as it pleases. If there would be a real big crisis, other rules could be implemented, that nobody knows (suspension of trading etc.)

When it is a standard regulated SG broker and your ETFs are not composed of SWAP products (like XTrackes do), in case Your roboadvisor company goes broke, You should be refunded the remaining value.

Assuming you mean a controlled closure (not some sudden liquidation event that leaves a legal message on who owns what) - even if you get liquidated on your holdings, presumably you could take the money and find another platform/channel to invest again into similar funds so sure admin hassle and some frictional costs but you wouldn't lose a ton of money.