1.Bitcoin holding - Download bitcore from bitcoin.org - download whole blockchain make 3 keys backups(on 3 diffrent pendrives) and sync it once every 2 months.
2.Cardano Holding - Download DAEDALUS WALLET from cardano.org and rest like ^
3.BNB and BUSD - Holding it on Binance (Its centralised chain soo anyway it dosent really change anything)
4.Ethereum - create wallet on my ether wallet and make 3 backups on pendrives.(I wanted to download mist wallet but it dosent seems to working anymore)
(every wallet be offline all the time Only windows + wallet will be installed on the SSD each Wallet has separate PC).
Storing seeds and private keys digitally is not recommended. You should write it down on paper and store it in 3 separate geographical locations if possible. It's much easier to make backups of seeds than it is of private keys. Maybe it's worth considering using Electrum for your Bitcoin because with that app, you get a 12-word seed to back up. That's unless you are insisting on having a full-node client. If you have to use USB drives for sensitive data (again, not recommended), at least encrypt and/or password-protect the files.
Your wallets are not offline if your computers are connected to the internet and you use them to sync and download the latest blocks. Did I understand correctly that you are planning to use 4 different PCs for each of your wallet or are we talking about 4 SSDs on the same computer? And will those computers be used for any other activities besides holding your software wallets and syncing with the blockchain? Are they clean with freshly installed OSs or have you use them in the past for other stuff?
1.We are generating Seedphrase to Ledger not for Bitcoin,ethereum,bnb etc for example (Dosent that mean they have to store our btc/eth seeds somehow?)
Seeds and private keys remain on the device all all times. Ledger uses secure element chips in their hardware wallets, and sensitive data doesn't leave those chips. The seed is only shown to you once during the setup process. Once that is done and you have made a backup of it, you can't see it ever again. You can't see the seed in the native Ledger Live app.
2.What if they went bankrupt and software will be abadoned dosent that mean we wont have access to our funds?
No. Wallets that generate BIP-39 compatible seeds (like Ledger in this case) can be recovered in other software or hardware wallets. If your device breaks, Ledger ceases to exist as a company, or your computer where the software/hardware is used malfunctions, you have your seed backups to rely on. The Ledger is just a hardware device that keeps your private keys in the secure element and signs transactions for you.
3.Lets says i have keylogger or anything related to it on my Phone (And connect nano x with bluetooth) and i would like to send from ledger to exchange some BTCs dosent that mean "Virus" will be able to swap my sending address or generate new transaction to the hackers address?
Keyloggers don't swap addresses. They record and log your activities, like the things you write on your keyboard, they can take screenshots of what is on your screen, etc. This data gets stolen and sent to a malicious party. But like I mentioned above, your recovery phrase is never visible in a software environment, it never leaves the safety of the device, which means there is nothing for the keylogger to log. You also can't view or copy your private keys because they are also always on the secure element. So again, the keylogger has nothing to steal.
Clipboard malware is a different threat though. In theory, they can swap your legit address for one that belongs to a hacker. But that happens on a software level. When you make a transaction with a hardware wallet, all the information has to be checked and verified on the screen of that hardware device. Your malware can infect your computer, but I have never heard of a clipboard malware that can infect and modify the transaction details that are shown on the screen of your hardware wallet. Always confirm that the information is identical to what the Ledger shows. If you need to send a transaction to someone and you receive an address to pay to, a clipboard malware can replace that address when you copy it. When it's pasted into a software it can be a different address. It's your job to check that the pasted address (that will receive the coins) as well as the amounts and fees match with the one the other party gave you. If they don't, don't make the transaction. A hardware wallet can't protect you in this particular situation. If the other party makes a similar mistake and sends you the wrong BTC address, it's their fault.
4.And how can i verify thats while Ledger nano X During production didnt get any thing "additional"(by it workers not the company while compiling Ledger)
When we are talking about Ledger hardware wallets, you can't. The before-mentioned secure element chip is not open-source, which makes the firmware not open-source and the whole product closed-source.
