I highly recommended who got stuck at lv3 or 2 should play this game on freshnewgames.com. In that site, you just need to past 1 round and type "M" to past the other round ( remember beginning the battle 1st then "M" or it will lead to round 3 and you will stuck there) . I have finished this game in the site I recommend above quite easily thanks to "M". The main thing is that you have to try many way for every level- I used M in 4 stages but archer lv 2 or higher ( using bow) and white mage with heal skill is the key to success in the long run.
I've never used knight lv3 or 4 to past any level and I believe the team I mention above is the easiest to past the last 4 level