Hi banderas
First, "ahead of [the] ceremony" is correct; "ahead of the beginning ..." isn't because it's near redundant. Second, "ahead" collates with 'of time' more so than 'of [noun]':
1. You'd better be there ahead of time, before the opening ceremony. :tick:
2. You'd better be there ahead of the opening ceremony. :tick: (Meaning, before it starts)
Third, Khalid's example "ahead the ceremony" isn't correct, and Snowcake's example, "ahead of
the beginning" doesn't work.
:-D;-)