His black turtle neck was by St Croix. Sure he had 100 of them. Starting wearing then in 1999.
http://newsfeed.time.com/2011/10/06/brand-behind-steve-jobs-iconic-turtleneck-sees-sales-boost/
No.
http://newsfeed.time.com/2011/10/16/who-actually-designed-steve-jobs-famous-mock-turtlenecks/