IS this a finished Callistemon (Bottle Brush) flower

Pretty. I remember having a few plants that were hard to tell whether they were in bud or were finished (hardy Geranium comes to mind). But I think these are spent because all I see that's left are the calyxes and the pistils. See if you can identify any ones that haven't bloomed yet, the difference should be apparent & from then on it'll be easier to spot them. In any case you won't kill it by pruning off blossoms, at least not any more than you would by deadheading spent blooms....

You're more likely to kill it with kindness than anything else - they don't like to be cossetted so don't overwater it or overfeed it.

Australian plants, it'd make more sense to me to look at an Australian site. Try:

Yes, but there is no real hurry.

Thanks Guys :-)