No its not possible, minimum code coverage required - 75%. for classes - no limit, it can be be 0% also, for trigger - minimum 1% . Finally you need minimum 75% combined code coverage.
No - whichever way you choose to deploy your code to production will execute the unit tests (although there have been periods during upgrade windows in the past that have unintentionally allowed this).
You have to have 75% coverage of all code in your production instance - note that this doesn't mean each class needs 75% coverage, just that the average is 75%. So you could have a large class with 100% coverage that allows a number of smaller classes to be deployed with none - this isn't a good idea, as its best practice to write tests for your code. You also have to have *some* coverage for each trigger, again this doesn't mean 75%, just greater than zero.
Unit tests are a good thing - they make sure that your code still works when admins etc make changes to the configuration of the system. Without this, the code could be doing something entirely different to the original intention and nobody would be any the wiser.
You have to have 75% coverage of all code in your production instance - note that this doesn't mean each class needs 75% coverage, just that the average is 75%. So you could have a large class with 100% coverage that allows a number of smaller classes to be deployed with none - this isn't a good idea, as its best practice to write tests for your code. You also have to have *some* coverage for each trigger, again this doesn't mean 75%, just greater than zero.
Unit tests are a good thing - they make sure that your code still works when admins etc make changes to the configuration of the system. Without this, the code could be doing something entirely different to the original intention and nobody would be any the wiser.