HCP, so before the ledger live came out, there was no way for someone to test if their 24 word phrase was 100% correct even though everyone should make sure they wrote their 24 word phrase correct?
No, that isn't correct. Prior to Ledger Live there were still multiple ways to confirm if your 24 word phrase was correct...
1. you could note down the receive address... then wipe the device and restore it using your written down seed... then check the receive address. Same address == correct seed
2. You could restore the seed onto a different hardware wallet (ie. a second ledger or another BIP39/44 compatible hardware wallet like Trezor)... check that addresses match.
3. You could restore the seed into a BIP39 compatible software wallet (preferably offline)... and check the addresses generated match
4. You could test the seed using (an offline copy of) IanColeman's BIP39 mnemonic converter and check addresses generated
Obviously, some of these methods are more "secure" than others.
Also its 100% that installing that program and you entering the 24 word phrase would never be an issue right? When you put in the 24 word phrase, you are doing so from the ledger s so if your computer is hacked or malware, that protects you still right since you are manualy typing the 24 word phrase on your nano ledger s?
Theoretically yes. The data entry is on the device, so the computer being infected shouldn't matter. In fact, to be "extra" safe... you can actually connect the device to a USB charger, and initialise it that way... so it isn't even connected to a computer when you set it up.