The sentence is perfectly correct. What's more, there is no redundancy here. These are probably words to a song, and there is a nice rhythm to this line.

Yes, but you can also say : Nothing will ever be the same again.

I don't think it's wrong, but it's kind of redundant, 'nothing will ever be the same' already implies that it will not be what it used to, so I don't think it's needed to add 'as it used to be'. I am not a native so I am not 100% sure, but I have never heard anyone say that. Just 'nothing will ever be the same' or 'nothing will ever be the same again'.

yea u can say that