#2 is fine re repetition, but the comma produces a comma-splice sentence. Insert a conjunction, or change the comma to a semicolon (and add a comma after 'instead').
#3 & 4 -- You needn't repeat 'theatres'. Both the singulars and plurals of 'size' and 'form' work, as they can be considered either countables or concepts. In #3, you need to repunctuate 'small, circular or octagonal' to avoid its reading as three different choices: 'small, and circular or octagonal'.