There is not much difference between these levels. If you can avoid blundering pieces you should be able to get a 1000+ rating.
how long should it take to get from 600 to700 elo
It depends how much you've learned. A player who can play at 1000+ rating should be able to do it in a few hours. A player who can only play at 600 rating might take much longer because they have to learn more to advance.
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