What is 999999999999ULL
These values appear for the regtest chain only.

It looks like these values are supposed to state the time window during which deployment of a particular protocol change is allowed to happen. For regtest that window is set to be from times 0 to 999999999999, maybe so that you can do it whenever you want.

For your coin, you presumably either want these features active from day 1, or not at all. In either case you'll probably want to remove the time-deployment code altogether.