Rinse shrimp, pat dry, keep shells on.
Fill a large pot two-thirds full with water.
Add Old Bay, squeezed lemons, garlic, bay leaves, peppercorns, salt, and beer.
Bring to a rolling boil, let boil 5 minutes.
Add all shrimp, stir to submerge.
Wait for the water to return to a boil.
Cook exactly 2 minutes after the boil resumes.
Drain immediately.
Transfer to an ice water bath for 2 minutes.
Drain and place on a platter.
Sprinkle with more Old Bay and lemon juice.
Serve with cocktail sauce and melted butter.