Corrected entry: When the women are talking about Becky's visit, Sophia refers to Dorothy as "The president of knocked up and single." Other episodes established that Dorothy became pregnant when dating her ex-husband, Stan, in high school. She had all of her children with Stan, so she has never been a single pregnant woman.
Wham, Bam, Thank You, Mammy - S6-E5
Corrected entry: Blanche's nanny remembers seeing Blanche in a white dress at her wedding. But in a different episode, Blanche celebrates her anniversary by trying on her RED wedding dress. She explains that even she couldn't keep a straight face in a white dress.
Correction: Mammy's exact words are "Did you or did you not wear your first formal white dress with pink flowers to your junior prom". She was not talking about Blanche's wedding.
Corrected entry: Blanche's brother tells of his and his boyfriend's plan of a simple ceremony. The year is 1990 and Florida didn't recognize gay civil unions or anything like that back then.
Correction: Whether it's officially legal or not, a couple can still organize a ceremony and treat it as a wedding. The brother and his boyfriend would consider themselves married.
Correction: Technically if you're not married, legally, you're single. She hadn't been dating Stan, just slept with him. In all the discussions about what happened, before her marrying Stan, she stated she went with him on a date, not that they were officially dating.
Yes, according to the episode "What a Difference a Date Makes" (Season Six), Dorothy agreed to a drive-in movie with Stan because she was upset after her date for the senior prom never came to her house (she was unaware that he did come, but Sophia thought he was not good enough for Dorothy and told him to leave). She and Stan were not a "serious" or "steady" couple at school, apparently.