Is this the only thing one should say on Laylatul Qadr
No. This statement of the Prophet, on him be peace, does not mean this is the only du’a one should make.
It means this is the very best prayer we can utter in this incomparable moment because it condenses all that we seek from Allah — on this holiest of nights and in the whole of our lives — in just seven words: divine pardon for our sins and failings so He cleanses us, by His grace, rendering us worthy of admission to His Gardens of Paradise.
It is best also because this du’a is perfect in its manner and structure, as well as in its content for this destiny-altering Night. It entreats Allah with the exemplary etiquette and sequence of accepted supplication:
First, it acknowledges Him alone with humility.
Next, it beseeches Him only with intense sincerity by the action of one of His Beautiful Names.
Then, it extols the superabundance with which He copiously showers His loving, kind mercy upon all His creation.
Only lastly does it entreat His gracious clemency on His servant, who is now in beautiful surrender.
This, then, is a peerlessly packed and perfect prayer for a singular illuminated night. Only the Prophet, on him be peace, could have uttered it. It is Revelation.
As to the question of devotions in this time, one should fill the night of Laylatul Qadr with worship: supplications, Allah’s remembrances (dhikr), Quran recitation, and — above all — Ṣalâh (Prayer).
The Prophet, on him be peace, said: