if you sell something for $1 at 10am your $1 still buys $1 at 10pm.

This is untrue for pretty much everything, even fiat. Everything is a market. A good example of this: stocks.

in crypto, it's easily manipulated, and that's by design.

Now this is just false. You’re just inventing fake facts here. You clearly know nothing of the history of crypto.

If I sell 1BT worth of something at 10am, it could be worth 2BT at 10pm, but it could also be worth .1BT equally.

Uhh no? 1 BTC will always be 1 BTC. Its value compared to other assets will change though. And in that case it would have less value indeed. You’re just allergic to high variations and high risks assets. Stocks is exactly the same. Some assets vary more than others. Let me assure you the value of BTC will never do a +/-10x in a day

tell me, what governing body or economy is crypto backed by?

Emission (POW, POS…) (or total stock), demand and offer and perceived value, just like everything on earth?