How to create two-week recurring alarms and reminders?

Solution 1:

The app you are looking for is Due which can set up repeating reminders as you have described, AND (most importantly) it can repeat its reminder alarm every X minutes until it is marked "done" (at which point it will reset for the next occurrence). I use this for reminding me to take out the trash, which needs to be done every other Wednesday, for example.

Solution 2:

Both macOS and iOS support "custom" repeat intervals that are somewhat flexible.

Based on reading your clarification, it doesn't sound like you need anything beyond a simple 2-week repeat interval per event but you may need more than one event if the days for the event occurrences in even-numbered weeks are not the same as the days for the event occurrences in odd-numbered weeks.

When creating a new event (see image below), select the repeat option. On the repeat menu, select the Custom... option. Set the frequency to weekly, but set the repeat interval to 2 weeks and then select the day(s) of the week for that particular event.

In the image below I repeat the event on just one day per week, but it is possible to select multiple days.

If an event occurs on one set of days in odd number weeks (week 1, 3, 5, etc.) but it occurs on different days in event number weeks (week 2, 4, 6, etc.) then you would likely need to clone your event from week one to create a new event for week two ... and then set the repeats for those at 2-week frequencies.