I would say (I'm not a native speaker, so it's just guessing here) that they are not. I think you would be perfectly understood without shortening them. But I think some shortenings are more commonly used, and the Germans are so accustomed to them, that if you want to better "fit in" with your language, you will have to learn to use them ; D
It seems a little weird as in "the home", it seems as if anything is should be "the house" instaid of "the home" because "the home" makes it sound like its your home and "the house" sounds like it is a random house or at least someone elses house, home refers to your house, which house on the other hand makes it sound like your snooping someone elses house!?
This might be a bit of Americanism, but I think we would say here, "we go by the house". The translated sentence above makes it sound like you took the long way around the house (as in a circle) to avoid the house. "By the house" would imply something like, "about the area" or "nearby" the house.
um / um ... herum = around
As a preposition, um has different translations into English, depending on context.
E.g.: Es geht um die Sache. = It is about the issue.
Sie kümmert sich um das (= ums) Haus. = She takes care of the house.
And um can also be a conjunction:
E.g.: Er kommt, um zu helfen. = He comes in order to help.
You're talking about how two way prepositions work. When we use a two way preposition such as 'unter, in', the dative case is used if the object is in a fixed position while the accusative is used when there is movement from one place to another. In this sentence, we make use of the accusative preposition 'um' so that means that whenever in a sentence you have 'um' or any other accusative preposition, the rest of the sentence will be in the accusative case.
Two way prepositions work like this: Sie ist in der Bäckerei ( She is in the bakery) Now in this sentence we know that the woman is in the bakery, that means that there's no movement, so we make use of the dative case.
Sie geht in die Bäckerei ( She goes in the bakery/She is going in the bakery ) Here, the woman is going into the bakery so there's movement, that's why we use 'die' (accusative case)
Hope this helps!
The translation for the discussion states "We are going around the house" but the answer claims "We go round the house" is the accepted. This is misleading to me because those are two different phrases. Going "around" the house is either literally circling the physical building or going room by room through it. Going "round" the house seems to be more saying "we are going by the house" as a stop along the way to somewhere else. I chose the latter since "um" can mean "by". Or at least I thought...any clarification or is DL just being DL?
I don't know which "the list" you mean, but perhaps because it's not a widely used word in modern German.
There is wider den tierischen Ernst but in general, wider ist most often used as a prefix in forming other words (e.g. Widerstand), and only rarely as a preposition. gegen is more common in the sense "against".
Thank you for your explanation. My husband and I initially learned German 35+ years ago and languages do evolve. The list at the beginning of the Duolingo preposition module has accusative, dative and 2-way prepositions. https://www.duolingo.com/skill/de/Accusative-Prepositions. In the Dartmouth German Review website, "wider" is givens as a seventh accusative preposition.. http://www.dartmouth.edu/~deutsch/Grammatik/Grammatik.html