about how many samples of moon rock have been brought back to earth?

The number of "pieces" of rock brough back by the Apollo missions (six missions) is officially 2,415 and each piece was called a "sample" at the time.

If we add the Soviet samples (326 kg, compared to the Apollo program's 382 kg), we could double this number to around 4,000 for all humans. (But we do not have an actual number for the Soviet pieces).

Since then, many pieces have been cut up in lots of tiny pieces, each one becoming a "sample" for analysis in some lab.

But your question is clearly how many have been brought back and that is a bit more than 2,000 but a lot less than 2,000,000.

Total moon rocks brought back by NASA is about 420Kiligramms.

Soviet Union also brought few gram sample from moon by automatic sample return misions

Several hundred pounds of Moon rocks have been returned by both the Apollo astronauts and by one or more unmanned Russian probes. The chemical analysis of the American and Russian samples showed many similarities.

The question is meaningless. Six missions brought back material, amounting in total to some hundreds of kilograms; how it was divided up into samples isn't meaningful.

d: None, landing were a probe with a boot.