Church Slavonic in principle should be pronounced phonetically, exactly as it is written, and in general you will hear его pronounced yegó, with no V sound, or Svyatágo (Holy) and not Svyatóva as in modern Russian.
In practice, clergy may slip some modern pronunciation within Church Slavonic, like unstressed O with an A sound, but that is generally frowned upon.
For understanding: http://www.russianlessons.net/lessons/lesson10_main.php
For quick reference: https://en.m.wikipedia.org/wiki/Russian_declension
In this sentence I am missing a particle for it to mean "to have".
In previous lessons I read things like "у тибя ест молоко" or something like that. The "ест" was signalling to be that this was to have, or had, or belonging to someone. Now there is not such word or particle so to me it reads smth like "The child does not/is not milk".
I hope my question makes sense.
The Russian is fine, but the English is incorrect. "This boy has no milk", "This boy doesn't have milk" are the English you need. You cannot just say "he" for this boy unless you're physically pointing at him (which Duo cannot see). Also, just because he has no milk doesn't mean he needs milk.
I put "the boy does not have milk." And duolingo marked it wrong. This is happening more and more and is very frustrating.
Duo wants to make sure that you understand that этот means this. There are occasions where you can get away with using the if it carries the same meaning but obviously Duo doesn't think it applies in this example.
Duo will never mark you wrong for taking the various forms это to mean this. They will mark it wrong a good deal of the time if you replace it with the. By doing so, Duo will help you remember the difference even if you don't yet understand it. Of course, you may find that frustrating.