I'm assuming you mean it's a fixed rate that increasing on the 22nd, a change in rate wouldn't usually involve going back to underwriters as the application would have been stress tested day one and allow for increases to a certain extent. A new loan is just issued either ahead of time or with the drawdown cheque.
If the Homebond is a condition of drawdown on the loan offer then I doubt you will be able to draw down without it, is there the possibility of partially drawing down before getting it which might or might not secure the rate, need to ask, some banks only do partial drawdowns on variable and issue fixed on final drawdown.