You will need funds in account to place Buy order for ITC, not having funds will result in your order getting rejected due to insufficient funds.
Also, Liquidbees cannot be sold after market hours.
Yes, your entire margin can come from Liquidbees as these are considered as cash equivalent. But this margin cannot be used to settle your losses or charges arising from trading, for that you will need cash in your account.
For Q2, Q3, everything has been explained in detail here: Everything you need to know about Liquid Exchange Traded Funds (ETFs)
Price of Liquidbees stays constant at 1000, looking at fluctuations in charts isn’t of any help.
The process to pledge securitues you are holding has been explained in detail here.
You will be able to pledge securitues only after they are credited to your Demat account on T+2 days.