Re: Marlin Error code 'fpos_t' after 'struct'

errors are:
SdBaseFile.h:199: error: 'fpos_t1' has not been declared
SdBaseFile.h:203: error: 'fpos_t1' has not been declared

somewhere between your first post and this one you have changed fpos_t to fpos_t1

but it looks like you have missed one or broken it.

there is a section near the beginning of the SdBaseFile.h file that should looks like

struct fpos_t1 {
/** stream position */
uint32_t position;
/** cluster for position */
uint32_t cluster;
fpos_t1() : position(0), cluster(0) {}
};

I'm guessing you have an error in this area, in particular in the name fpos_t1 (from the error in the first line of this section)