Does a divorce occur by saying "You are divorced" via a mobile phone message, and is an 'iddah (waiting period) and a new marriage contract required for reconciliation, and is reconciliation permissible without the wife's consent during the 'iddah?

Divorce via a mobile message is a written divorce, which does not take effect unless intended. If you did not intend divorce, it does not occur. But if you did intend it, then it has occurred. You may take your wife back before her 'iddah (waiting period) expires (three menstrual cycles for those who menstruate, or three months for others) without the condition of her knowledge or consent. If her 'iddah has ended, then a new marriage contract, with all its pillars, is necessary.