What you mention are the bugs that occurred in version 0.7.0 and have been fixed in 7.1 and 7.2.
The Yuna thing you mean level 3 and you can only do it once Anna lives with you and you can level up Yuna (Yuna's level is locked at level 2 until Anna moves in with you). Playing v7.0 (which no one should have) you can break the girls. In this case, even breaking the game (when I was researching), I was able to do that task without any problems (it's something I've tested recently).
Mara's I have to add a better description as it has more requirements, not just level 5 (you need Anna and Yuna's sexiness unlocked or you will never be able to do the task).
The rank thing is a bit weird because just by talking to Maria when she forces you to do the rank quests if you exceed what she asks you (for example you have 6 but she asks you for 5 proof of trust) the quest should be updated correctly to be able to advance.
Having changed the experience table was something that at first seemed like a simple thing without problems but has brought catastrophic consequences that fortunately in 7.2 is "all" solved (as long as you have not abused the potions ignoring the mechanics of the girls).