Where is transactions which was sended on nonexistent adress? Where are stored btc, if we send it on nonexistent adress?
There is no such thing as a "non-existent" address... Bitcoin addresses are classified as either "valid" or "invalid".
"Valid" means the checksum passes and that the Base58check encoding is OK. eg: 1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2
"Invalid" means that the checksum fails and that the Base58check encoding is incorrect. eg: 1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN
XYou can check validity here:
http://lenschulwitz.com/base58The network does not care, nor can it "know", if any given "valid" Bitcoin address actually belongs to anyone or is in "use"... Think about the situation where someone has create an offline paper wallet using dice... how would the Bitcoin network know about the address for this wallet? It can't... so it doesn't care... if the address is valid, any bitcoins sent to the address will be assigned to it... regardless of whether or not anyone actually has the private key for it.