Please take time to familiarise yourself with THE PASSOVER HAGADDAH (in advance) before PESACH SHENI [starts at sun-set Monday 26th April 2021 (Iyyar 14)].
So, the first Seder is on Monday 26th April 2021 evening and the second is on Tuesday 27th April 2021 evening.
For those observing the whole 8 days, the last day is: Iyyar 22 (sun-set Tuesday 4th May 2021). It is after this that you can bring back the leaven products into your home 🏡.
The following link will give you all the information you need to know about Passover: