Is turning the necessary movement for apparition?

Question

In the Harry Potter series, every single time a character apparates they turn on the spot. When Twycross teaches this, he doesn't mention turning anywhere. It seems implied that is part of apparition.

‘The important things to remember when Apparating are the three Ds!’ said Twycross. ‘Destination, Determination, Deliberation!

‘Step one: fix your mind firmly upon the desired destination,’ said Twycross. ‘In this case, the interior of your hoop. Kindly concentrate upon that destination now.’

Everybody looked around furtively, to check that everyone else was staring into their hoop, then hastily did as they were told. Harry gazed at the circular patch of dusty floor enclosed by his hoop and tried hard to think of nothing else. This proved impossible, as he couldn’t stop puzzling over what Malfoy was doing that needed lookouts.

‘Step two,’ said Twycross, ‘focus your determination to occupy the visualized space! Let your yearning to enter it flood from your mind to every particle of your body!’

Harry glanced around surreptitiously. A little way to his left, Ernie Macmillan was contemplating his hoop so hard that his face had turned pink; it looked as though he was straining to lay a Quaffle-sized egg. Harry bit back a laugh and hastily returned his gaze to his own hoop.

‘Step three,’ called Twycross, ‘and only when I give the command … turn on the spot, feeling your way into nothingness, moving with deliberation! On my command, now … one –’ > Harry glanced around again; lots of people were looking positively alarmed at being asked to Apparate so quickly.

‘– two –’ Harry tried to fix his thoughts on his hoop again; he had already forgotten what the three Ds stood for.

‘– THREE!’

Harry spun on the spot, lost his balance, and nearly fell over. He was not the only one. The whole Hall was suddenly full of staggering people; Neville was flat on his back; Ernie Macmillan, on the other hand, had done a kind of pirouetting leap into his hoop and looked momentarily thrilled, until he caught sight of Dean Thomas roaring with laughter at him.

‘Never mind, never mind,’ said Twycross dryly, who did not seem to have expected anything better. ‘Adjust your hoops, please, and back to your original positions …’

. . .

Twycross stepped forwards, turned gracefully on the spot with his arms outstretched, and vanished in a swirl of robes, reappearing at the back of the Hall.

‘Remember the three Ds,’ he said, ‘and try again … one – two – three –’

Harry Potter and the Half-Blood Prince

So my question is: Can you succeed in apparition if you don't turn but still do something involving movement?

Answer 1

In a word, yes. Dumbledore is pretty much the most powerful wizard there is, and even he needs to turn in order to apparate. We see this a couple of times in Harry Potter and the Half-Blood Prince.

‘Very good,’ said Dumbledore. ‘Well, here we go.’

Harry felt Dumbledore’s arm twist away from him and redoubled his grip: the next thing he knew, everything went black; he was being pressed very hard from all directions; he could not breathe, there were iron bands tightening around his chest; his eyeballs were being forced back into his head; his eardrums were being pushed deeper into his skull, and then –

and

‘It will not be necessary for us to enter,’ muttered Dumbledore, glancing around. ‘As long as nobody sees us go … now place your hand upon my arm, Harry. There is no need to grip too hard, I am merely guiding you. On the count of three – one … two … three …’

Harry turned. At once, there was that horrible sensation that he was being squeezed through a thick rubber tube