if you make such program for free if not we can discuss this if you want you can contact me on telegram its same as my username since i am not that active.
You should be a little bit more clear if you want someone's services. I've understood half of what you wrote.
To generate a private key take SHA256(string + n), where n is an ASCII-coded number that starts from 1 and increments as additional keys are needed.
And
string a random hexadecimally represented number? If you just want to generate brute forcefully addresses starting from a random number, just increase it by 1 for each loop.
I want the above functionality with a simple twist since gpu will generate addresses in millions compressed and uncompressed form similar to vanity address generators save only the addresses
Would you mind telling us what's your purpose? It seems like you want to recover lost funds.