Long Term Capital Gains Tax and Koinly

I have some questions related to weekly DCA purchasing and cost tracking. From what I have researched, I need to get Koinly (or something similar) to assist with this tracking for tax purposes, so I am in the process of obtaining that right now. I am in the U.S.

Questions regarding Koinly:

1) Once I link my coinbase account, does Koinly go through my transaction history on the exchange and assist with past purchase tracking or does it only work for purchases going forward? Basically, if I purchased it now, could it help track BTC purchase from previous years as well as ongoing?

2) If I don't use something like Koinly, do I have to manually figure out the cost/exchange rate of every single transaction on a first in first out (FIFO) basis? If all of those DCA purchases have been moved off the exchange and into another wallet, they are still all tied to their original costs and FIFO, correct?

Other questions:

3) If I hodl for ~20 years, am I still going to need to know the exact costs/exchange rates of these weekly DCA purchases (20 years prior) when I eventually sell?

I'm not planning on selling anytime soon, I'm just wondering how much harder it will be to track all of these things if I don't start tracking now. Thanks.