If the opening price is 4.5c on Tuesday, that means we've had a...

If the opening price is 4.5c on Tuesday, that means we've had a pretty good announcement

Seriously though, yes, it means all buy offers below 4.5c would not have processed after the opening auction. All buy offers at 4.6c and above and all the sell offers at 4.4c and below would have been processed and balanced out at 4.5c.

If you access the CommSec platform on a desktop, you will be able to scroll through the market depth to see every buy/sell level. Based on your screenshot, no one has a bid on at 4.5c yet. So if you are the first bidder at 4.5c and it opens at that price, then yes, you would have bought at least some shares at said price.

Hope that helps and good luck with your purchase!