What happens after the last spin
This is the part most no deposit bonus banners skip. When your final free spin lands, the casino adds up what the spins won and credits it as bonus money. From that moment the offer behaves like a small free chip: you bet the balance on eligible games until you've met the wagering, and the max bet rule applies to every spin.
Here's a worked example using HellSpin's listed terms. Say your 30 spins win A$6. At 40x, you now need to bet A$240 in total before the balance becomes withdrawable. At A$0.50 a spin that's 480 spins. If the balance survives and grows to A$70, the A$50 cap means A$50 is paid and A$20 is removed. If it drops to zero along the way, the offer simply ends and you've lost nothing of your own.
Run the same sum on any free spins no deposit Australian casino offer before you claim it. The same A$6 at Ripper's 60x would mean A$360 of betting, and the cap would be five times the bonus, so A$30. Same spins count, very different finish line. That's why the cards show wagering and the cap next to the spin count, and why our guide to win limits is worth a read before your first claim.
Does the game matter?
It does, but only for the spins themselves. You can't change the pokie, so look it up before you claim. A high-volatility game like Book of Dead or Elvis Frog in Vegas can pay nothing for twenty spins and then land a large feature. A lower-volatility game spreads small wins more evenly. Neither is better; they just give the no deposit bonus a different feel.