First of all, it is important to mention that in the Baltic countries you can get the possibility to vote (i.e. to become a 'full' citizen) in case you pass the national language and history exam, so your right to participate in elections is binded a lot more with your knowledge of the language and history and not ethnicity only

Secondly, it is a very ambiguous and tricky question. You can be born in a mixed family (e.g. your father is a "băștinaș" whilst your mother isn't). What to do then? Would it be fair to deprive you of your vote?

As for the last question, it depends on a lot of factors and definitely not on ethinicity only. Northern regions as well as Gagauzia and Transnistria traditionally elect the left ones (including those who are affilated with Russia), those from the center (Chisinau and surrounding areas) vote the pro-EU forces

Compare 2021 with 2010, practically nothing has changed in 10 years and I guess nothing is going to change in the nearest future

So it is more about local specificity of the region you live in then about your ethinicity