1. The appeal before high court may take a longer time, depending on how and when it reaches and other formalities.
2. The chances to win the case through appeal is very bleak as per the grounds of your divorce petition.
3. Yes, you are right that after the respondent enter appearance and file counter, the matter will be taken up for arguments straight away
4. It is not necessary that the high court has to uphold the judgment of the lower court, it will analyse the facts and points put forth in the memorandum of appeal, counter and arguments made by both the aparties, before taking a decision.
5. Your grounds for seeking divorce appears to be very weak. In my opinion you may file a divorce petition afresh with fresh cause of action on the grounds of desertion and mental cruelty instead of preferring appeal which may not be a wise decision especially when the grounds for divorce are very feeble and unjustified or not conforming to the provisions of law in this regard.