What is the standard as to whether an item is “discoverable” in a case?

You are sitting at your desk at your job when a mail carrier comes in and asks the receptionist to sign a receipt for a certified letter. Upon opening the letter, the receptionist discovers a complaint filed against the company. YOU ARE BEING SUED! After a few deep breaths you call the company attorney who informs you of the company’s rights and duties as a defendant in a lawsuit. Months later, as your company is firmly involved in the lawsuit, your receptionist again is asked to sign a receipt for a certified letter. This time it is a Motion to Compel Discovery and it asks the company to produce for the defendant a copy of every written document in the company’s possession and for a full copy of the company’s computer hard drives, emails and other electronic files. Again, you do the right thing and call the attorney.
1.What is the standard as to whether an item is “discoverable” in a case?
2.What are your rights and duties as a defendant, in regards to potential evidence, upon being served with the complaint in a lawsuit?
3.Are you allowed to delete, destroy, shred any electronic or physical documents upon being served with a lawsuit? What are the consequences if you do? Is there a defense for having previously deleted email or electronic documents?
4.Is the plaintiff allowed to ask for a copy of everything you have? What is the standard? What would be your response?
5.Is the plaintiff allowed to ask for a copy of your hard drive? What protections can be put in place for your data?
6.What about your social media and that of the other employees? Is that discoverable?