For example, if bitcoin is going to crash and I exchanged it into $1200 Ethereum lets say. And it goes down to $800 USD, will the Ethereum value go down?
Could you exchange your bitcoin into another currency to be protected from a crash?
I think Coins like Doge, LTC , USDCOIN all of these are 99.9% stable always in the same price, 0.01% prob that you are very very very unlucky and it drop when you buy but I don't think it will happen.
What do you think ?
if bitcoin goes down to $800 you should buy as much as you can in my opinion because first of all it won't go that low second of all that would be a good opportunity to buy cheap coins before it goes back up.
but if you want to invest in other altcoins you certainly can but it is not wise at all to invest in altcoins such as ethereum that are manipulated and are getting pump and dumped.
p.s. you need to see some charts by the way because the prices of coins you named (i don't know what the hell USDCOIN is) have never been stable.