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I wouldn’t start any hard studying too early as it might put a strain on your ‘memory retention’ abilities but it’s ultimately up to you.
You can definitely start some light reading to familiarize yourself with what’s to come.
If you do decide to start early, a study plan would definitely be a MUST. And lots of constant revision to ensure you don’t forget what you have learnt in reading 1 by the time you hit reading 10. For me, what works is to revise previous topics before I start a new one. With all the constant revision, it will become anchored in some part of your brain and even if you don’t know its there, its actually there.