Ukrainians can hear the difference between ‘g’ and ‘h’. Both sounds exist and easily recognisable. For example in ‘hlib’ (bread) and ‘gora’ (mountain) transcripted as ‘hora’ in Latin alphabet. Ukrainian ‘g’ is voiced glottal fricative that exists in other Slavic languages and non-Slavic languages : https://en.wikipedia.org/wiki/Voiced_glottal_fricative
Ukrainian is not second most spoken Slavic language. As already pointed half of Ukraine speaks Russian. Many Ukrainians speak ‘surzhyk’ which is a mixture of Ukrainian and Russian. https://en.wikipedia.org/wiki/Surzhyk
Ukrainian being voted most melodic language after Italian in Paris is a myth. Similar myths exist about Belarusian and Estonian languages being voted second most melodic languages after French in Paris.
Expression similar to ‘ta ni’ exists in colloquial Australian English ‘Yeah no ‘ https://minerva-access.unimelb.edu.au/handle/11343/39316
Probably in other English languages.
In the Ukraine would mean in some region. In Ukraine means in the country. It became a subject of a discussion in independent Ukraine. Similarly, Ukrainians don’t like when Russians and Poles say ‘na Ukraine’ (some region) rather than ‘v Ukraine’.