1. You can access the money any time you have a medical bill, you can either pay for it with your HSA issued debit card, or pay for it by other means and submit the receipt later. This also means that as long as you save your medical receipts, you can delay submission as long as you want. These transactions are tax free.
2. Once you reach the age of 60 or 65 (can't remember), you can withdraw funds just like a 401k, but it would be taxed if not spent on medical expenses.
3. It depends on your provider, lots of HSAs allow you to invest in vanguard index funds
4. + 5. Yes to both, and completely tax free if spent on medical expenses