You can sell LIQUIDBEES anytime during the market hours. As per SEBIs upfront margin requirements, when you sell shares from holdings, you will get 80% of the sell proceeds on the same day. The remaining 20% is blocked for the day under delivery margin field and will be available from the next day. You can learn more on this here.
Brokerage for delivery trades is 0. Also, there is no STT applicable on LiquidBees, but other charges like ETT, Stamp Duty will be applicable.
1 day returns will be very miniscule. Considering the statutory charges, it might not be profitable. You can check the current returns of LiquidBees here: Nippon India ETF Nifty 1D Rate Liquid BeES: Check NAV, Portfolio & Returns | Nippon India Mutual Fund
You can learn more about Liquid ETFs here: Everything you need to know about Liquid Exchange Traded Funds (ETFs)
This is a mandatory requirement from SEBI to ensure brokers do not misuse funds and/or securities kept with them. You can check this post for more information: New Running Account Settlement Rule - Single day for clients of all stockbrokers in India