1. 'Ever' means 'at any time', and is the opposite of never (no time). You can use it with any tense. 'Do you ever drink whisky?' 'Very occasionally'. 'Do you think that people will ever live on the moon?' 'No, never. It's impossible.' 'Ever' is the correct word to use with your example about Japan. The usual way to ask this question is: 'Have you ever been to Japan?' 'No, I've never been to Japan. But I have been to Korea.' 2. 'Already' and 'yet' are related in meaning. 'Yet' is usually used in questions and negatives, while 'already' is mostly used in affirmative sentences. Have you had lunch yet? No, I haven't. I'm really hungry. or Do you want some lunch? No, thanks. I've already eaten. I can understand your confusion, as all three of these words can translate into Portuguese as 'já'. It might be helpful for you to think of 'yet' and 'already' as the English equivalents of 'já' (though with different grammatical uses). The English word 'ever' has a different meaning (approximately 'alguma vez' in Portuguese) , but remember that this is the word we use to talk about life experiences - as in your question 'Have you ever been to Japan?' Please ask if anything still isn't clear.

Replace 'in' with 'to' and the sentences makes sense.