The 1929 postmark above is inscribed in Cyrillic at the top for KARASUBAZAR, the original Tatar name for a place now called Bilohirsk (in Ukrainian) and Belogorsk (in Russian). The postmark is bi-lingual and at the bottom is inscribed in Arabic.
The 1930 postmark is in Russian at the top with a soft sign after the CH (Google tells me that in Ukrainian there would be no soft sign). The International R label on this letter transliterates the place name as KERTCH though in English-language sources it is now normally spelled KERCH. But at the bottom we have KERC in Latin script and this could be post-Ataturk Turkic - though Google has the name with a cedilla in order to indicate the soft "Ch" pronunciation: KERÇ
This 1940 Soviet postmark for SIMFEROPOL also gives the city its Tatar name AQMESCID in Latin script.
Finally, here is one where I have hit Google without success (I tried for Jewish / Karaite communities too). At the top we have what looks like KADISH and at the bottom QAD S or QAD 5 in Latin script. This is one my readers must solve. Postscript: And Vasilis Opsimos has solved it. See his Comment which identifies Kadish as present-day Voronky.
Added February 2020: Most of my Ukraine-related Blog posts are now available in full colour book form. To find out more follow the link:
Kadish is present-day village of Voronky (Воронки́) in north-west Crimea (Razdolnensky rayon).