The phrase espero que is a subjunctive trigger, so anything after it should be in the present subjunctive. One thing to note, however, is that if it's the same subject (I hope I can or I hope I play etc), then you simply say espero poder or espero jugar etc. Since here you're saying I hope it will be fun (first subject is I and second is it) then it would be espero que sea divertido.
Espero que sea divertido is the one when you express a wish for the future.
Esperaba que fuera divertido (pero no lo fue) : I was hoping it was fun (but it wasn't) when you use ESPERAR, DESEAR, PREFERIR, NECESITAR in the past. Therefore, it triggers the need for imperfect subjunctive.
Don't use fuere. It's a very old form that isn't used in Spanish any more . You only see it in "old" literature or in sayings such as: donde fueres haz lo que vieres (when in Rome, do what Romans do)
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