I'm graduating this semester and have opportunities a few "top" software companies (e.g. Amazon, Microsoft, Google). I've had two internships: one with a government contractor and one with Amazon.com. At Amazon I worked on some pretty cool stuff, received a return offer, and above all, worked ~8 hours a day. However, I feel like my experience as an intern may have been significantly different than a full time employee because of "on-call" and other full-time responsibilities. So, I have a few naive questions about the software engineering industry as an employee that I hope some of you may entertain:

(Note: I have no debt.)

1) I want to work for a start-up or lead one myself in the next 4-5 years. Is it realistic to take a job at one of the large firms, build capital for a few years, and then take a dive into the risky start-up world?

2) Is Google still the premier job for a graduating software engineer? Are the perks and culture still strong enough to trump opportunities at a company like Amazon?

3) Work/life balance is very important to me if I'm not working at a start-up. Is it unrealistic to expect to work ~8 hours a day at these software giants?

4) Finally, what general advice would you send to a 21-22 year old entering the industry with a solid resume?

Thanks to anyone who takes the time to answer any of these questions.

*) TL;DR: If you could start your software career from scratch, what would you do differently/the same?