Is it permissible to ask one's wife about sins she committed while she was away from her husband, and is she allowed to conceal them, and does the husband have the right to inquire about that whenever he has a doubt?

You have no right to question your wife about her past or recent sins or their details, nor should she inform you of them. Every human is a sinner, and the best of sinners are those who repent. Furthermore, the Messenger (peace be upon him) commanded covering sins and not publicizing them. You must assume the best intention, avoid doubts and spying. If anything suspicious arises from her, then separate from her without revealing her secrets. You are part of the problem by accepting your wife's stay in Western countries at a young age without a guardian. Your duty, if you wish to maintain your marriage and turn a new leaf, is to try to rectify this situation, either by her coming to you or by you going to her.