Make Dough: In large bowl, place butter, yeast, granulated sugar, milk, and 1 egg. Add 3 1/4 cups flour, poppy seeds, salt, and baking soda. Using hands, bring ingredients together to form cohesive dough. Sprinkle some of remaining 1/4 cup flour on work surface and knead dough until soft but not sticky, adding a little extra flour if necessary. Transfer to clean bowl, cover tightly with plastic wrap and refrigerate 2 hr. or up to 12 hr. Make Filling: In bowl, combine butter, brown sugar, and cinnamon. Make Frosting: In bowl, place cream cheese and sift confectioners’ sugar over top. Add vanilla, lemon zest, and lemon juice and mix to combine. Leave at room temp up to 3 hr. or refrigerate up to 12 hr. Lightly dust work surface with flour. Roll dough into 12- by 16-in. rectangle. Spread with cinnamon mixture and scatter blueberries on top. Starting from long end, roll dough into tight log. Cut log into 8 pieces and transfer to 9- by 13-in. baking dish; let rise at room temp until rolls touch and are puffed and no longer cool to the touch, 1 1/2 hr.  Heat oven to 375°F. Lightly beat remaining egg and gently brush all over tops and sides of rolls. Bake until rolls are light golden brown inside, 30 to 35 min., covering with foil if outer parts begin to brown too quickly. Transfer to wire rack. Spread with cream cheese frosting and sprinkle with poppy seeds if desired.