What happens when someone sends LTC to a BTC address and suppose it says success ?
It's always preferable you send cryptos into their required wallet address. It's not advisable you send your cryptos into other non compatible wallet address just like sending Bitcoin Cash into Bitcoin Wallet address or sending etherium into Dash wallet address. Every crypto has it's wallet address and you are required to send such crypt into their wallet address. It doesn't take much time to generate crypto wallet addresses and I suggest you generate a wallet for LTC and send your Litecoins into your LTC wallet address instead of risking it with your BTC wallet address.
Does that really go through the blockchain on LTC?
I don't really think so because every crypto blockchain differs from each other and they are also controlled or operated by different people. You can't compare Bitcoin blockchain to Litecoin block chain just like you can't compare steem blockchain to etherium blockchain. There is high chance you loose your LTC if sent into another blockchain apart from LTC because it may not go through the LTC blockchain.
The best way you can achieve this is by converting your crypto into the crypto you intend to store in the blockchain. What I mean by this is that if you intend to store your LTC into BTC wallet address, it's advisable to convert your LTC into BTC so that it automatically gets stored into the BTC blockchain.
How can an invalid LTC address will execute the transaction through blockchain ?
The fact is that every wallet address you generate on the blockchain are already programmed and encrypted from the blockchain. This is why you can generate BTC wallet address in different websites or Apps and they tend to exist irrespective of where you generate them. This means that you can't just sit down and form any wallet address and expect it to exist on the crypto blockchain.
This also applies to LTC and other cryptos because you can't transact or store your cryptos in an invalid wallet address since it wasn't generated from the crypto blockchain.
Thanks for reading and I hope this helps.
I think it's pretty risky to do that in some sense. You could try but I think this transaction would get through but then it would get lost somewhere. There is usually a warning that is written before sending any transactions which states to check the transaction address that is to be sent. I don't think it would work as it would be like sending something to the wrong address.
Unless in the exchange system itself there is an internal exchange where we could convert the ltc to btc then it won't be much of a problem at all. I have tested something like this and it works usually.