To tackle your first question, I think it’s tricky to provide an objective timeline on national/cultural identity for Ukraine (and elsewhere), but there has certainly been talk amongst Ukrainian historians that Kyivan Rus’, as based around Kyiv, was Ukrainian as opposed to Russian (unlike what Russian historians, at least traditionally e.g. Karamzin 1816-29, asserted). In this traditional view, to Russia at least, the Ukraine was simply “Little Russia” and Belarus “White Russia”. Obviously, there were works - typically in Ukraine - which challenged this view. Hrushevs’kyi (1898) wrote of the distinct culture and development of the Ukrainian masses in the populist style of historical writing but I think more modern historians have argued that it must be taken with a pinch of salt - being populist, it inherently puts down the bourgeoisie and it has been argued he only stressed the negative impacts of Russia on Ukrainian history and identity (how far you agree on the negativity/positivity of Russia’s influence is up to you). Similarly, regarding Hrushevs’kyi, Plokhy (1995) has disputed the relevance of his work even in those regions he studied due to “Russification” and movement in those areas in more recent years.

There are obviously more nuanced studies of Ukrainian identity - in the nineteenth century, there were studies of the everyday Ukrainian woman although in 1929, Hrushevska pointed out that they were written from the point of view of elite men. Lately, more works have been written on gendered Ukrainian identity. There are also studies of regions and political beliefs - in the theme here of Russification, Hillis (2013) studied right bank Ukraine where there was some desire for the Russian influence - but we certainly can’t say this is representative of the Ukrainian people as a whole. More recently (20-30 years), there have been more studies on language and culture, more widely, and perhaps censorship has played a good part in calls for their separation from Russia (both in Tsarist and Soviet eras)...

Hopefully this has provided you with some new avenues to explore if you are interested in the topic, I’ve swept over it quite briefly as a short overview of the subject but I really find it quite fascinating and there is so much more to find! There are more and more sources on Ukrainian identity, and plenty of identities to search through which I haven’t even touched on, so have a look around at some academic papers!

Funnily enough, I did a piece for my degree this past academic year on Ukrainian identity which was focused on the Eighteenth Century. Some names to check out on the subject:

Bassin et al (2017), Plokhy (2001), Iakovenko (2002) on Russophile histories.

Kappeler (2009), Hillis (2013), Tairova-Yakovleva (2015), Vushko (2015/16) for the Spatial Turn.

Kuzio (2001), Zhuk (1995), Bessmertny and Gerevich on the Cultural turn more broadly (the latter focus on the Annales approach).

Shulman (1999), Brock (1972), Burkovs’kyi (1996) for language and culture

Hrushevs’kyi (1898), Korpovich, Doroshenko (1923), Ohloblyn (1966), Krupnyts’kyi, Pirie (1993), Horak (1965), Plokhy (1995), Wunot Jr. (1987), Mazour (1958) and Brükner (1987) for populism and criticism/praise of key populist works.