no
Raw shrimp cannot be refrozen. This is because the raw shrimp will get freezer burned and could grow harmful bacteria.
NO
because it can who told you that?
Shrimp should be blue if it's frozen raw. If it's been in the freezer for too long it will turn white (that means it's freezer burnt). It's still okay to cook if there are some white bits but I wouldn't cook it if the entire shrimp is white.
Cooked shrimp can be left out at room temperature for no more than two hours. After the two hours has passed, you either need to refrigerate the shrimp or throw it away. Shrimp left out on ice will last much longer.
Yes
It's never advisable to re-freeze raw meat once it has been defrosted especially sea food - the worse kind of food poisoning is from sea food. Shop bought shrimp are generally safe to freeze immediatly after purchase, but once defrosted, they are exposed to harmful bacteria which can spoil them, and therefore they cannot be refrozen. Defrosted shrimp should be covered and stored in the fridge, and consumed within two days. -The following is from the UK Food Standards agency - http://www.eatwell.gov.uk/asksam/healthydiet/fiasandshellfishq/#A221177 When you buy prawns from a supermarket or fishmonger, they might have been frozen before, even if they aren't frozen when you buy them. Check the label or ask the person serving you, if you're not sure. You shouldn't freeze prawns that have already been defrosted.
Sure... but it will more then likely be over cooked. Shrimp does not take long to cook. Your shrimps texture may be a little tough. But YES, you can fry pre-cooked shrimp.
Shrimp cocktail is not cooked, though the shrimps will be par boiled and cleaned before you add your sauce
For shrimp ceviche I suggest the website Simplyrecipes.com. The recipe is very well written, easy to follow and has pictures of what the ceviche should look like. Just remember that with shrimp ceviche, the shrimp will need cooked slightly before making it because the acids will not cook the shrimp or get rid of bacteria like they do when using fish.
The recommended amount of shrimp per person is 1 pound of raw shrimp or 1.2 pound of cooked. For 60 people you would need 60 pounds of raw or 30 pounds of cooked shrimp.