1) is a cliche at this point, to the extent that this 2015 listicle has a huge variety of figures both new and old:

https://www.pcmag.com/news/tech-ceos-who-ditched-college-for...

2) WhatsApp founder Brian Acton was famously rejected by Facebook (and Twitter), and is the canonical example, but there are others. There's even a website:

https://rejected.us