I tot buddha attain enlightenment via awareness of breathing
meditation?
Before the Buddha reached Awakening and attained the Three
Knowledges, he primarily practised mindfulness of
breath meditation (Anapanasati), and he practised it
frequently after his Awakening too.
From the Dipa Sutta : The Lamp
http://www.accesstoinsight.org/tipitaka/sn/sn54/sn54.008.than.html
"This is how concentration through mindfulness of in-&-out
breathing is developed & pursued so as to be of great fruit, of
great benefit.
"I, too, monks, before
my awakening, when I was an unawakened bodhisatta, frequently
remained with this abiding. When I frequently remained with
this abiding, neither my body was fatigued nor were my eyes, and my
mind, through lack of clinging/sustenance, was released from
fermentations.
From the Icchānaṅgala Sutta
http://www.accesstoinsight.org/lib/study/recollections.html#passage_40
Then the Blessed One, emerging from his seclusion after three
months' time, addressed the monks: "Monks, if wanderers of other
sects should ask you, 'With what abiding did Master Gotama often
remain during the Rains retreat?' — thus asked, you should answer
them: 'The Blessed One
often remained with concentration through in-&-out breathing
during the Rains retreat'...
"Monks, if anyone speaking rightly were to described something
as 'a noble dwelling,' 'a brahma-dwelling,' 'the Tathagata's
dwelling,' he would, speaking rightly, describe concentration
through mindfulness of in-&-out breathing as 'a noble
dwelling,' 'a brahma-dwelling,' 'the Tathagata's dwelling.'
"Those monks who are trainees, yearning for the unexcelled
relief from bondage, their aspirations as yet unfulfilled: for them
concentration through mindfulness of in-&-out breathing, when
developed & pursued, leads to the ending of the
fermentations.
"As for those monks
who are worthy ones, devoid of fermentations — who have attained
completion, finished the task, laid down the burden, attained the
true goal, destroyed the fetters of becoming, and are released
through right knowledge: for them concentration through mindfulness
of in-&-out breathing, when developed & pursued, leads to a
pleasant dwelling here & now, and to mindfulness &
alertness.
"If anyone speaking rightly were to described something as 'a
noble dwelling,' 'a brahma-dwelling,' 'the Tathagata's dwelling,'
he would, speaking rightly, describe concentration through
mindfulness of in-&-out breathing as 'a noble dwelling,' 'a
brahma-dwelling,' 'the Tathagata's dwelling.'"
And also, the Maha-Saccaka
Sutta describes how the Buddha attained his Three
Knowledges 