Please post your location so that one of the forum members may refer you to a Tax consultant in your locality. Consult and register with PSEB to prevent headaches and get better advice. They have done a lot to make this process relatively headache free for freelancers.
I'll try to answer your points based on what I know for sure. (Only for the ones I'm sure about)
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Keep your invoices and receipts scanned and handy.
You've been paying taxes since the day you were born
, you just need to 'file' for the past two years and pay any outstanding taxes for those two years' income.
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I'm sure you have spent on things or services where tax was deducted and you can get a receipt for that and in some cases a tax deduction certificate as well. For example your ISP, mobile operators, restaurants with proper POS systems in place , Cash & carry stores (try to do all your shopping there, everyone deducts GST but only good Cash & Carry stores give details of deducted taxes on receipts)...
I hope you get the idea and this helps in some way.
If I find out more about the remaining points, I will post here.