There is no such word as "Руссия". Country is always "Россия" and adjectives are "русский" (nationality) and "российский" (citizenship).
The letter "У" instead of "О" comes from the fact that our country was called "Русь" a long time ago. Thus you have a nationality "русские", but there are not only russians living in modern Russia. We have plenty of other nationalities.
Russia is a federation like US and in some parts of it there are two official languages. For example Tatarstan republic has Russian and Tatar. These languages are both "российские" but only one of them is "русский".
"There is" is usually translated into Russian as "существует" or "есть". For example:
- There is a problem - существует/есть проблема
- There is a squirrel on the tree - на дереве белка (The word "есть" is obvious and thus skipped)
- There is a squirrel sitting on the tree - на дереве сидит белка (gerund replaces the verb "есть" in Russian)
P.s. I am not sure that sentence "There is Russia" does really have any meaning. Correct me if I'm wrong.
It would change the meaning a bit. When you say "Там Россия" - it's the direct order, so there is definitely a verb omitted. Full phrase is implied: "Россия [находится] там"
If you change the order you may also mean some different accent:
- "Там [находится] Россия" - same meaning
- "Там [была] Россия" - past tense
- "Там [именно] Россия [,а не другая страна]" - More probable English translation would become: "It's Russia over there" (not another country)
But still the difference is so vague that I'd advise you to report an error if Duo doesn't accept that.
There cannot be any dispute here:
Here is directly translated as здесь/тут
There is directly translated as там
I don't know what case you're talking about, but perhaps Duolingo sometimes accepts both translations as correct since these two words (both in English and Russian) have quite close meaning.