Starting from the first question, asking someone to translate a sentence (any words really, but a full sentence certainly) without showing them what any of the words mean first is not helpful. Things should be at least introduced before you assume people will have any capacity to answer questions related to them.
That's why you give it a try and if you're wrong, you'll know the next time. Language is more than just a set of rules. It's sometimes more helpful to learn phrases and sentences than to memorize grammar. That way you can get AWAY from the temptation to apply your own language's patterns to another language that does not function that way. And it's exactly this step AWAY from pure grammar that has made DuoLingo so popular.
You still have to learn the missing pieces of grammar to realize that, but by using something that is not that easily discernible makes it harder to learn the right way to understand a phrase. I'm not advocating for pure grammar as you've stated, but rather a reasonable scaffolding of knowledge.
I believe adding a Russian keyboard at this level would be crucial. I have typed what I have heard, in English letter, as "Tom, Tim Tam" and would've loved to try guessing how to write them (and other basic words/sentences) in Cyrillic script. I think that way one would get familiarized faster and better to the alphabet.
Other than that, I am intrigued by the sentence structure. I think it would be better for me to compare it to Arabic where one can similarly say, if translated literally, "Tim Doctor" and "Tim there?" without having a specific word for "To be".
In Russian, the verb "to be" is ommited when the sentence is in the present. As there were no other verbs to be found, it can be deduced that the verb of this sentence is the verb to be. So... "Tom, Tim there?" becomes "Tom, IS Tim there?", as this is the only place to fit the verb.
Funny, when one uses just "there" it gives "Another solution" with "over there". So I used it here and it's wrong...