I am absolutely crashing out trying to figure out the differences between
行かなければいけません、行かなくてはいけません、and the ならない variants. My dashboard taught me these plus the contracted forms, but I cannot figure out which version the machine wants because it will only accept one right answer. Anyone have any tips? Other than just memorize the set sentences from this app?
You’re better off memorizing the grammar point description under the question rather than the sentences themselves but yes, reasonable crashout. We’ve all been there hahaha.
For these specifically I just hit backspace and wrote in the specific type they were asking for as long as I knew I was choosing one correct version. The only real difference is the register, just commit one polite and one casual one to memory.
From experience, in casual speech people mostly use 行かなきゃいけない or 行かないといけない (and often even remove the いけない).
Confused about the difference between なくては and なければ so I’m mostly guessing anytime one of these questions comes up. Thankfully in real life they seem relatively interchangeable and the exam is multi-choice.
All of these structures for “have to” are just various combinations of “If I don’t ___ then it’s bad”. In these two cases it’s just conjugating the negative part ない to the “if” statements ては and れば. If it’s not immediately obvious it’s because using ては as “if” is technically an N2 grammar point so you won’t see it for a while.
But essentially you’re right, they’re interchangeable so don’t worry.
This application I also think is uniquely bad at teaching these grammar points because it will only accept one of the variations. It literally just told me, “can you make it more casual?” and the answer was the "ならなおい” variant which is only used in formal settings T_T
Feel free to ignore me. I am just ranting.
I believe in this case by “more casual” content team meant “give me plain form, not ます form”. You were supposed to figure it out from the “Standard” hint above the question.
Of course it’s not helpful that 2 different terms are used to request this.
Bunpro needs to me more consistent with words “polite”, “formal”, “casual”, “standard”, “less polite” and “less formal”, “more casual” and such.
Well if it doesn’t you just type the one that you remember, and won’t learn the other versions 
If they could improve Bunpro in a way, I would love if these pages had a link to a little list of versions ranged on politeness.
Like
Or
This way they all get the same place in your brain, and you can easily pick out what you need to go for if things need to get more or less formal.