Crypto Tax Laws Aus and Cashout Method

Fast forward 6 months since my last crypto post and miraculously I've made some huge, HUGE gains in crypto!

As i was 16 at the time, I could not buy crypto so I mined $20 and since the past 2 weeks it has gone an unbelievable x1000! I got lucky because I put it all on PAC coin in the doge market and when it went past subsatoshi into the BTC market it exploded!

Now I am finding a suitable way to cashout. Honestly, as I am young and stupid, I have already cashed out a few K's worth using livingroomofsatoshi and did not consider tax. Do I have to worry about declaring that small amount since I am still under 18?
I have been researching, and me trading crypto means I need to pay CGT but from what I understand it is assessed as bonus income and if your annual income for the year is less than $18000, you don't need to pay tax. Does that mean I can withdraw freefully until the 18K threshold??
Also, if it does come to declaring my taxes, they require you to keep all transaction but I have hundreds of trades and I cannot understand how I can record all taxable events.

In addition to that my exchange, Cryptopia is pretty crappy and does not show the historical price at which I initially purchased the coin, only a timestamp, could I make up the prices according to historical snapshots on coinmarketcap? Could I maybe only declare that I've earned about 18K and withdraw all and not have to pay tax?

I need all the help I can get in this exiting field and now that I have a decent portfolio the next target is that Mil. Please if any accountants could give me some advice would be really appriciated :)

TLDR: Made serious money with crypto and don't know the cashout process, I'm also under 18