The principle is the same. There is no way to know the public key if all we have is the hash from the corresponding address. Either the public key has to be revealed in the output script or the owner of the address has to spend from it and reveal the public key.

In this case the owner has spent the shitcoins they received as an airdrop on a poor copy of bitcoin and its blockchain called bcash. But they never spent their bitcoins so we know the corresponding public key from that shitcoin's blockchain: https://blockchair.com/bitcoin-cash/transaction/6e8b59f6e9f3c472df0b40ec8742f61d3e8af3678b3568a14a047317be320ffa

This is partly because of a bug in block explorers where they show P2PK outputs (that already contain the public key) as a P2PKH address. If you check the first received transaction in this "address" here you can clearly see that the payment was to the public key (ie. a P2PK output) so we already know the public key.

There is also some payments to the actual P2PKH address that uses the has of the public key (1JqPFnGPhHhy54zJKmC1MPiczzgFjCmzE9) but the block explorer shows all txs under the same address.
So if you search the public key of the said address, what the tools do is that they simply look up that P2PK output and return its public key which makes it look like they guessed it from the hash!

It depends on the address or output type. There is only one address type that uses public key directly and that is the new P2TR address that uses the tweaked public key. Other addresses are using hash of the public key and since hash is irreversible we can not know the public key.
However, there are outputs scripts that can use the public key directly (they don't have any address defined). Like P2PK or P2MS outputs or anything similar that uses public keys.

It depends on the client that create the wallet file and the type of the wallet.
For example a watch only wallet that only received the address to watch will not have the public key but a wallet that was created from a private key or deterministic wallet created from a seed will have both private and the public key in addition to the script type of the addresses created by that wallet.

If you have created the wallet file yourself then you already know that it is the real thing but if you have bought it or found it somewhere then you should be sure that it is a fake thing possibly containing malware.