Answers to date questions.
1. Sicily, Cefalu, Bishop's Palace. The backwards Cs (and the matching forward C) are here represented by round brackets.
The date is "( I ) I ) CCVIIC", which can be re-written MDCCVIIC. The unorthodox approach is at the right-hand end: VII has to be read as 7, and subtracted from the final C to give 93. So the date is 1000+500+200+93 = 1793.
2. The Roman numerals, extracted from the Latin inscription, are:
I + D + M + V + V + I + V + I + I + V + I + I + I + I + V + I + C + I = 1635
3. The dates on the facade of the church are similarly worked out:
C + C + L + M + I + I + I + D + L = 1803
C + I + C + L + I + I + I + V + D + C + D + D + I + V = 1865