Rokiškis 1943

This is a registered mail sent in 1943 from Rokischken (now Rokiškis, Lithuania) to Wien also under German occupation. Michel calls Rokiškis, "Rakischki" but the correct official German name during WWII was Rokischken. I wouldn't say it is "wrong" because there are several sources that mention about the name Rakischki especially during the WWI period, probably coming from the Polish name Rakiszki. It has a nice arrival cancellation of Wien on the back.

Vilnius 1920

Unfortunately one stamp is missing but this is a registered postal stationery with added stamps sent on 21 June 1920 from Wilno (now Vilnius, Lithuania) to France. Prior to the formation of Central Lithuania, the Poles occupied Vilnius from 19 April 1919 to 13 July 1920, this card has been used during this period.
It is addressed to a certain Madame A. Hock in Gueugnon in the department of Saône-et-Loire in France but later redirected to Uriage (Uriage-les-Bains) in the department of Isère, which is known to be a spa town. The sender's name Helene Kwasser also doesn't seem Russian (rather German sounding) but their correspondence is clearly in Russian. Hôtel du Gare does not seem to exist in present Uriage anymore.

Vilnius 1937

This is a maximum card of Józef Piłsudski, the Chief of State of the Polish Second Republic, cancelled in Wilno (Vilnius, Lithuania) in 1937 with a commemorative postmark of the exhibition of the 10th anniversary of Radio Wilno, known as "Radio dla miasta i wsi" (Radio for cities and villages) at that time. It was the first permanent radio station in Vilnius. The following year in 1938, the Polish Radio released a publication about the contents of the exhibition which, thanks to the Polish National Digital Library, we are able to see. Here is the link.

Palanga 1943

This is a stampless official use registered cover sent in 1943 from Polangen (now Palanga, Lithuania) to Berlin, Germany. The sender is the Dienstpostzweigamt Polangen, a branch of Dienstpost Ostland post offices which was the postal authority of the region during the German occupation in large part of Lithuania. The term "postlagernd" is the equivalent of Poste-restante.

Gilandviršiai 1914

 Queen Louise Bridge, the border between Sovietsk and Panemunė

 Sterpeiken (now Strepeikiai, Lithuania), 9.21 1914

 Gillandwirszen (center) and Sterpeiken (left) on a 1861 map

This is a German military field post (Feldpost) card sent in 1914 from Gillandwirszen (now Gilandviršiai, Lithuania). According to the list of post offices of Memelgebiet provided by Michel Deutschland Spezial, the post office of Gillandwirszen has closed down on the 1st of December 1923. The postmark on the scan with the inscription "Kr. Tilsit" has been used during pre-Memelgebiet period as well as after the Treaty of Versaille along with the newly created postmark with the inscription "Memelgebiet". Gillandwirszen has been later incorporated into Kreis Pogegen and during Nazi re-annexation into Kreis Tilsit-Ragnit. Today, Gilandviršiai is part of Tauragės apskritis/Tauragė county with the population of 55 according to 2001 census. If you look closely to the card, the author actually wrote it in Sterpeiken (now Strepeikiai) which is a village right next to Gillandwirszen.
The picture on the card is Queen Louise Bridge which linked Tilsit (now Sovietsk, Russia) and Übermemel (now Panemunė, Lithuania) over the Memel (Nemunas in Lithuanian) river. It has been named after the Queen Louise who resided at the city of Memel (now Klaipėda, Lithuania) when it served as the temporary capital of the kingdom of Prussia during the Napoleonic wars. The bridge still exists today and serves as the Russo-Lithuanian border.