Extract substrings from given strings according to a given list of sets of numbers (N, i, n) step by step.
Start with an empty string.
For each number set, extract n characters starting from the i-th character of the N-th string with N and i being in 0-based indexing, and append the extracted substring to the string.
Repeat the process until the end of the list starting from the first element of the list.

Provide the final string along with the intermediate strings after each process in a list.
Do not include the initial state and final state in the list of intermediate states. 
