Freezing apple juice kills no germs; only pasteurizing does this. Both only keep a couple weeks in the refrigerator until becoming ‘fizzy’. However we’ve kept it frozen well over a year with no trouble.
There are two questions here and the answers are No and No.
If apple juice is pasteurised in an airtight bottle it should contain few if any living organisms and should keep for several years. When opened it will inevitably be exposed to mould and yeast spores which everywhere swirl in the air, and, again inevitably, deterioration will begin. If the juice is kept in the fridge it may be a month, or even more, before anything visible happens. But happen it will, mould may grow on the surface, tendril-like objects may appear in the liquid, fermentation may manifest itself, the viscosity may change and eventually the juice will turn into something akin vinegar. If you drink it in the early stages of its deterioration it will merely taste unpleasant. The test is: if it smells and tastes all right – it almost certainly is all right. Just about the only danger that might pass through pasteurisation is metal contamination. There is a lot of acid in apple juice and for that reason it is best to keep it away from any metal apart from stainless steel.
Apple juice stored in a deep freeze will keep for a very long time; the most fastidious amongst us can detect no deterioration after a year. However, if the juice is allowed to come up to fridge temperature it is likely to start to go off rather more quickly than that which has been pasteurised. Juice that has been frozen straight from the press will have in it yeast spores, and, whilst these are inactivated in the deep-freeze, they are not killed; and even at temperatures as low as 3°C they may come to life again. Thus, after a week or two in the fridge, you may detect signs of fermentation. If drunk, apple juice in a state of active fermentation is said to have a laxative effect. If left alone the juice may turn straight to cider, or it may develop some of the undesirable symptoms described above. It is, of course, just as liable to suffer from metal contamination as pasteurised juice. It has also one additional hazard. If the original apples were allowed to come into contact with manure or other filth, they may have picked up the spores of something really nasty, and, though these spores might survive freezing, it is unlikely they would survive pasteurisation.
But do no worry. Treat your apple juice with a bit of common sense and it will do you nothing but good.