1

just get your ticket at the dock for those types of ferry runs

2

As above, just check online what time you want to catch the ferry between Cebu and Bohol and turn up at the ferry terminal about 40 minutes before and get your ticket and go.
As for Caticlan to Boracay theres a ferry every few minutes..

3

Thank you very much for clarification.

4

it can get very busy at Christmas, once I only just managed to get two tickets for the 30th of January Cebu-Ormoc Super Cat ferry and got one of the very last tickets available. One of us had to go business class, so the other ticket must have been the very last, normal class ticket. This was about three days, before it sailed.

the Super Cat's so called online booking service does not seem to work very well. But you can buy tickets in advance at many travel agents shops. If I was like arriving on the 17th December, and looking to get say, a Cebu-Tagbilaran ferry on like the 23rd or 30th, I'd get on it straight away.

at almost all other times apart from Christmas and Easter (and festivals, like Sinulog) you'll be ok just turning up at the port about an hour before. Beware, because a lot of passenger ferries have been known to sail overloaded at this time, though this is something the coastguard and port authorities have been cracking down on better recently.