Bro, you should cool down, you are the one talking it farther than necessary with too many philosophical relations to simple things. However, let me try my best to answer your questions.
So, we all say that hodling is better than trading, yeah? And I think the only way to earn from cryptocurrency is by exchanging it for fiat currency, right?
Of course, HODLing is better than trading. It's not in earning but the risk involved. You will gain more in trading if you know it, but the HODLing is safer, which makes people term it better. But you are wrong in the second part, you can only exchange your fiat for cryptocurrency and own it before you can profit from it. Not the other way round. The moment you exchange your cryptocurrency for fiat, you are divesting it.
Meaning, the hodling is just for the value to increase over a while and then you still trade it right?
I think the terms trading and investment are causing confusion here, but note, the two could be used interchangeably. At times, before you invest, trading must first occur. The moment you exchanged your fiat for cryptocurrency, you just traded. But keeping it without trading it further on the futures/margin market means that you're actually investing it.
And for the altcoins, after buying altcoins, what happens if no one wants to buy them from you? You know a lot of altcoins aren't all that popular so how do people even sell off their altcoins?
This is why you should not go for shitcoins. I will not dare to buy the altcoin I won't easily be able to exchange through popular exchanges. And I sell off those they enlisted initially and later delisted. The good part is that they announce it before making such a move.
Can you even hodl altcoins?
Of course! Anything you can do with Bitcoin can also be done with altcoins. Imagine buying Solana in 2022, you would have made at least 20 times your investment provided you keep it till now. Is that not HODLing? HODLing is buying your asset and keeping it for a long duration of time.