Creating 20 striped candies in 30 moves means that one striped candy need to be created per move. Hence, the only way to do this is to create at least colour bomb + striped candy combination. This can be difficult as cascades can very easily set special candies off or ruin combinations. Also, if you do not get rid of the chocolate and liquorice locks, it will ruin your plans. Get rid of them as fast as you can for space.
You may need to waste the first few moves in clearing the blockers.
Five candy colours will help you create the colour bombs and striped candies you need, but it will also create more cascades which ruins the possibility of creating colour bomb + striped candy combinations.
The presence of five colours makes it easy to create special candies. However, it is not too useful as the available board space at the start is limited.
The order is worth 80,000 points. Hence, an additional 100,000 points for two stars and an additional 200,000 points for three stars have to be earned through matching of candies.
Clearing the liquorice locks to increase available board space reduces the number of moves, aggravating the problem of meeting the order and getting three stars. Moreover, the chocolate will spread and may reduce available board space if not cleared quickly.
It is quite hard to create colour bombs and even if they are created, most of them have to be matched with striped candies to meet the order, largely reducing the number of colour bombs created for the purpose of boosting the score.
Compounding the above point is that the colour bomb + striped candy combination has to be done many times. Since points are not awarded for creating the combination, it means that players will only earn few points from just the striped candies.