Custom `create index` functionality specification in sqlite3

Question

I am looking to add my own functionality of an automatic index values in sqlite. While I look at create index sql statement here https://www.sqlite.org/lang_createindex.html I see that that is a restriction of getting any other details other than the current row values. I have two questions:

• Can I merge the create index statement with any other sql statement results to my partial index or normal index function?
• Second, Can I add my own c code for my own code that can get pointers to data, etc? The sqlite3.h and sqlite3.c does not have an AUTOINCREMENT function export. What is the code I move to add another optional function called CREATEINDEX that adds my personal indexing code? I will prefer to use this option. Where do I get the developer docs for pointers and cursor movement data type, etc. Say creating a function like this https://stackoverflow.com/a/28875809/3204942

#ifdef __cplusplus
extern "C" {
#endif
    /* 
     * Now declarations of C functions, such as extern int printf()
     * or whatever 
     *
     */
#ifdef __cplusplus
}
#endif

The only third alternative I can see is add my own code from the application. I have looked at prepare statement which can also be one option https://stackoverflow.com/a/7625848/3204942 , https://sqlite.org/c3ref/prepare.html , https://sqlite.org/c3ref/prepare.html