Missable Missions:
==================
.---------.-----------------.
|Mission: |Can Unlock When: |
|=========|=================|
| 1-2-1 | Chapter 3 |
| 2-1-1 | Chapter 4 |
| 2-1-2 | Chapter 4 |
| 2-1-3 | Chapter 5 |
| 2-1-4 | Chapter 5 |
| 2-1-5 | Chapter 6 |
| 2-1-6 | Chapter 6 |
| 4-3-1 | Chapter 6 |
| 4-3-2 | Chapter 6 |
| 4-3-3 | Chapter 6 |
| 4-3-4 | Chapter 6 |
| 4-3-5 | Chapter 6 |
| 4-3-6 | Chapter 6 |
| 6-2-1 | Chapter 6 |
| 7-1-1 | Chapter 5 |
| 8-2-1 | Chapter 4 |
'---------'-----------------'
The Missions above become unavailable when you go to Nibelheim. In other words,
you must finish them while you're still in Midgar in Chapter 8 (or sooner).