The top tier colleges and universities do not have online degrees. Harvard has a continuing education program (
Harvard Extension School), but you can't receive a BA entirely online. You can apply some classes towards the BA but would need actual classroom time somewhere to complete it. The extension school has open enrollment; you don't have to apply to take courses.
(Also, keep in mind that GPA is only one of many factors that affect admissions to elite colleges. Top schools like Harvard, Princeton, Stanford, and Yale reject more students with 4.0s in honors classes than they accept every year!)