Is it necessary for me to attend all three nights of laylat al-Qadr to achieve the big reward mentioned in the holy Quran?
What if I only attend one night?
And what if I decide to attend for only two hours?

And what tells us that the program provided for us on those three nights are sufficient to acheive the reward?

It’s not necessary to attend all 3 nights, but if you do, you’ll get a greater reward. If you can attend only 1 night then attend the night of the 23rd it’s the most important one.

And yes you can attend for 2 hours only. When you go back home, try to continue worshipping Allah. You only get this chance once a year, so make the best of it by repenting, supplicating, reading Qur’an, and reading Dua Jawashan al-Kabir.