(I want to try to build my own blockchain).
Are you building your own blockchain as in "a new type of coin", or just wallet software to interact with existing blockchain, e.g. Bitcoin? It sounds like the latter.
- How can i receive coins from other wallet addresses ( ex: ETH Chain or BTC Chain ).
To receive coins you need to create a valid private-public key pair, you keep the private key and give the sender your public key (typically in a hashed version we call "address"). The important thing is to be able to spend the coins later, which is what the private key is for.
- How can i check validity of that coin ?
Technically you check the whole blockchain to see where those coins originated and verify that all transactions and blocks are valid.
- What I'm receiving and storing in my database ?
It's up to you - you store what you need. At the very least you would probably store the raw transactions and some decoded info that allows you to verify them quickly. You can also store a list of addresses and balances and other stuff it more usable as a "ledger". It really depends on what you need.
- How to check that "Hashes" in other systems ?
Assuming you're talking about block hash - you hash the same info (block header, transactions) with the same algorithm (e.g. SHA-256) and you verify if your hash is the same value as the one you're verifying and meets the difficulty requirements.
I couldn't find any answer on those questions, only I could find is only concept of how blockchain works.
It looks like you stopped reading too soon. There is plenty of resources, e.g.
Bitcoin wiki, that would answer the above questions and more.
