Yes
M = 1000 none of the other letters are Roman numerals
The Roman numeral of MDCCCVII means 1000+800+7 = 1807
It means that the numeral is to be multiplied 1000 times and also numerals within brackets indicate multiplication by a 1000.
The Roman numeral of MLXVI means 1000+60+6 = 1066
That is not a valid Roman numeral.
M = 1000 none of the other letters are Roman numerals
The Roman numeral of MDCCCVII means 1000+800+7 = 1807
It means that the numeral is to be multiplied 1000 times and also numerals within brackets indicate multiplication by a 1000.
Not a proper Roman numeral
That is not a valid Roman numeral.
That is not a valid Roman numeral.
The Roman numeral of MLXVI means 1000+60+6 = 1066
Exactly as in the question but if you mean in Roman numerals then it is (V) which means 1000*5 = 5000
DDXCIX is not a real Roman numeral. D = 500 and DD if it existed would mean 500 + 500, which is 1000 but there is a Roman numeral for 1000, which is M, so the combination of DD would never be used. The numeral should be written as MXCIX and it represents 1099.
The Roman numeral M represents 1000. In ancient Roman use it did not always mean 1000, but it does today.
In Roman numerals XVII = 17
IVIIXIV is not a valid Roman numeral.