if you have so little time you should concentrate on just one opening against e4 and one against d4. and for the study plan... there is no universal study plan. Just make sure to solve a few tactics every day and with the rest of the time do whatever you like.
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I'm 1600 cfc and fide. I have an hour or so everyday set aside for chess. What would be a good study program 4 me. I play d4 as white and against d4 I play Slav or KID. Against e4 I play car Jann or Scandinavian. Money isn't a major factor.