What is the normal trial period?

In Germany, the “trial period” (Probezeit) for new drivers normally lasts 2 years from the day you first get your driving licence. That’s why answer 1 is correct.

The idea is that during these first 2 years the authorities react more strictly to certain violations to reduce beginner-driver risk. If you commit a serious violation (an “A violation”) or two less serious ones (two “B violations”), you usually have to take an advanced training course (Aufbauseminar), and the trial period is extended by 2 more years (so it becomes 4 years total). Also, alcohol or drug offences are treated especially strictly during this time.

Rule of thumb for similar questions: Default is 2 years; it only gets longer if you trigger measures through violations.