Early exercise / 83(b) has another benefit that most people aren't aware of -- if the exit is at least 5 years out, you can exclude 100% of your gain from federal cap gains tax under IRS Section 1202.
No, it's at the discretion of the company. I asked for an 83(b) option at a 10 person startup I worked at and the CEO made it happen. The startup still went under so it didn't matter in the end, but management definitely did what they could for the employees.
See here for more: https://blog.wealthfront.com/qualified-small-business-stock-...