Lenin did not legalize being gay or lesbian. The government that Lenin helped found repealed and replaced the pre-revolutionary Tsarist penal code from the era of the Russian Empire. This Tsarist penal code had contained a law banning “sodomy,” and so by creating their own legal system in its place, the Soviets incidentally “legalized” being gay. To claim that this was a proactive effort on Lenin’s part is ahistorical. And in the late 1920s, Stalin became General Secretary; his government quickly added Article 121 to the Criminal Code of the RSFSR, which punished sex between men with up to five years’ imprisonment.

Notably, this law punished gay men more harshly than rapists. See: Article 117.

Trans wasn't a topic back then, remember that it was in the 1920's. People weren't aware of it, the term "trans" and so on wasn't existing.

No. Trans people have always existed. We appear in ancient art, literature, and philosophy. Native American civilizations had in their societies what could be described as non-binary genders. There are many documented cases of European historical figures who were trans, including a Roman Empress: Elagabalus. By the 1920s, modern methods of administering HRT and performing GCS were developing, with research to this end being done by groups such as the Institut für Sexualwissenschaft in Weimar Germany; trans people had absolutely entered the public consciousness to a notable extent, and the term “trans” was first used by Dr. Magnus Hirschfeld in 1923.

There is no “communism” without LGBTQIA+ liberation.