Do frozen juices lose their vitamins?

Not at all. Although fresh fruit is always better, frozen fruits have as much nutrients. Keep in mind that once you freeze your fruit, you must keep it frozen until you are ready to eat the fruits.

I sincerly don't know… Maybe the temperature can influences on the vitamins actions but at the same time I hope the answer is no because I have always drank frozen juices and discover now that it's not like I thought since ever, would sound way off.

Firstly, fresh is always best.
Unless you're picking the fruit yourself, you have no idea how old it is when you buy it.
Frozen fruit and vegetables are snap frozen straight are picking so are a good second option.
Secondly, you are better off eating whole fruit in preference to juice as it contains vital fibre and thus will be more filling while have less calories

Well in my opinion if the fruit were fresh squeezed then it can be froze and it might keep the vitamins. But if the juice is left outside to oxidate before that, it will lose most of its vitamins and it will turn into glucose.

No, frozen juices do not lose their vitamins. Rather freezing works well to keep the juice fresher. However fresh juice that slightly chilled contains a higher concentration of all vitamins, minerals and fibers. Always choose to squeeze your own freshly made juice everyday.

No, they don't. Now, I don't wanna be that kind of person, but just keep in mind that fiber is a lot more important that vitamin intake. Whole fruits are a lot better than juice in that regard, since they won't give you a sugar spike and will make you feel fuller for longer.

no they do not just like if you were to freeze meat just because the meat is frozen doesn't mean it lost its protein or vitamins

Depends on lots of factors. Fruits do get to oxidize once you open them. The quality depends on whether these are organic, they're vacuum sealed, they're left out on the counter or juiced and stored right away, & c.