Good Morning Pass covers all ?

Welcome seansoo! First of all: will you be using any of the Swiss rail passes, or another rail pass such as the Regional-Pass Bernese Oberland? In that case you should buy a regular ticket with the discounts provided by your rail pass, as that's cheaper than the Good Morning Ticket and allows you to travel without restricted times. Also note that the Good Morning ticket is valid from May 1 only.

The Good Morning Ticket can also be bought for other departure stations than Kleine Scheidegg, such as Interlaken Ost, but you can only use it for the uphill journey that leaves no later than 08.00 am from Kleine Scheidegg (in other words, you have to catch the train that leaves from Interlaken Ost at 06.35 am). Fares are listed here; timetables are here. This train arrives at the Jungfraujoch at 08.52 am, allowing a 3 hour visit before your descent. That's enough to see the highlights, although some will prefer a longer stay.

You can buy your Good Morning Ticket (or another discounted ticket to the Jungfraujoch, as mentioned before,) right before leaving at the railway station from Interlaken Ost. You don't have to make reservations online.