What does MCDXCII stands for in roman numrals?

Answer 1

1492 but it should be written as MCCCCLXXXXII or XMDII and not as MCDXCII

This is incorrect. "MCDXCII" is the proper way to write '1492' in Roman numerals.

1) No symbol is ever used more than three times to write a given number, so MCCCCLXXXXII is incorrect

2) X is 10 and M is 1000. No numeral should be subtracted from another numeral more than 10 times its value, so expressing 1990 as "XM" is incorrect. '1490' should be expressed as "MCDXC".

"MCDXCII" therefore stands for '1492' in Roman numerals.