Unless you have another Account or are also playing on console, I only see one Level 43 non-Season Crusader on the Americas Region. (None on Europe or Asia Regions).
Are you playing in Campaign Mode or Adventure Mode? (Assuming you have Diablo III and Reaper of Souls).
Looking at your Career tab, it doesn’t look like you’ve fully completed any of the Act Quests (story-line).
In Campaign Mode, when you complete an area, the area is done. (Provided you’re completing the Quests along the way). You should also be able to return to areas you’ve previously visited by way of Waypoints.
However, you should not have to repeat Quests you’ve already done. Not unless you changed Game Difficulty. Or, if you change the Game Settings to an earlier Quest point, then you’ll have to repeat the Quests available from that point on. You will not lose any Achievements you’ve already earned.
So, unless you provide more information, I don’t know what to tell you.
You should also know: If you’re playing in Adventure Mode, you’re not playing the Diablo Story. You’re playing endgame content. Everything resets, maps and monsters, whenever you leave or quit the game. But, you can go anywhere you want to go without completing Quests first.