I’m pretty sure I read somewhere that Azriel is actually older than Cassian and Rhysand. I could be wrong but Rhysand is 535 years, Azriel is 537, and Cassian has been determined to be about 535-537 but someone calculated the ages and said Azriel is older than his brothers.
If you want acotar audiobook tho apps such as Libby or other online library apps and websites will have it. But this audio isn’t from the book and does not actually happen.