About 2 days, max,
If you keep iot in brine in fridge, at least a month
Feta Cheese Selection and StorageThe finest feta cheese should be purchased direct from its brine bath. If it is pre-packaged, it should have some of the brine in the packaging to keep it moist. Feta cheese is best when eaten fresh, so always check the date. If you will not be consuming it immediately, store feta cheese in a brine or milk bath. The milk bath will reduce the saltiness and help keep the cheese moist and mild in flavor. Properly stored in brine or milk and refrigerated, feta cheese will last up to 3 months. Feta cheese is not a candidate for freezing.
If it's in brine ( which is usual) then at least a month in the fridge.
It can be stored without brine for a very limited time
Mainly cow milk with a little salt and rennet.
Depends how careful you were when making it. I wouldn't keep such a thing more than 4 days even in fridge.
Unopened, feta has a shelf life of roughly 10 months from production. Opened shelf life is generally 4 - 6 weeks if stored properly. In order to get the longest life out of feta, wrap it in cellophane after each use and with new cellophane each time.
If it's in brine, you should not put it in the freezer at all.
About 4 - 5 days.
At least 4 months.
About 2,000 years
1 month max.