I apologize in advance if this is a stupid question, but I didn't go for this achievement equivalent in Reach. So I just want to be sure about how it works. For the solo Legendary achievement, do you have to do it a continuous playthrough? (Start to finish?) Or can you change the difficulty and play the levels in any order later on? Because I started the game on Legendary, but I couldn't beat it. So I dropped it down and enjoyed the game. Now I want to go back and finish it for the achievement. Do I have to replay the levels I've already beaten? Or can I just start on the next level I need to complete on Legendary?
For example, say I beat the first 3 missions on solo Legendary already. Can I just start the game up on solo Legendary on mission 4 and continue to the end for the achievement?
Thanks to anyone that answers my question. I appreciate the help. Also, here is a really helpful guide on how to beat the game solo on Legendary difficulty. It's what I'm going to use to help me beat it. Hopefully it can help others too.