If I reach my 401k limit of $16,500 in October do I lose out on the company match for the rest of the year?

It's best to spread it out over the entire year, but you don't lose out on any company matches if you don't.

When you stop contributing, the payroll system will also stop establishing a company match. At the end of the year, the 401K administration (the 401K like Fidelity, Principle, etc) that your employer uses, analyzes contributions and confirms the company match matched properly. If you are short, the money will be paid in but it could take a few months.

You end up with less since the match is on individual checks. You are best to spread the max out over the entire year.

The company match would be the same whether or not you hit $16500 in December or anytime earlier in the year.

Yes. High income earners should reduce the percentage so that the limit is not reached until the last paycheck.