You need to play the story to unlock the normal / hard / lunatic levels of the tower, floor 10 unlocks when you finish stage 9 of the story. You're saying you haven't even played the normal difficulty of the story mode, not even chapter 3 to unlock up to floor 4 ? Not even chapter 1 to unlock the first two floors ?? I mean, floors 1 and 2 are only worth it if you're under lv10, but for the whole tower to be locked, you haven't even finished chapter 1, why are you even thinking of these lv25/35 special maps ! Don't be lazy, do the story. It'll level you up past 25.
If I struggled to the end of my determination, to the end of my way of life with my followers, if the result is ruin, then this ruin is inevitable. Grieve. Shed tears. But you cannot regret.