Tayammum becomes invalid by everything that invalidates ablution.
It also becomes invalid with the removal of the excuse that permitted it.
If one can access water before starting the prayer, their Tayammum is void.
If one sees water during a prayer that does not exempt from making it up, like the prayer of a resident, the prayer is invalid according to the more correct opinion.
If one completed an obligatory prayer with Tayammum and then water became available after the Salam, their Tayammum is void, and they cannot perform a voluntary prayer with it.
One cannot pray with the same Tayammum except for one obligatory prayer.
It is permissible to combine an obligatory prayer with supererogatory prayers using it.
As for combining two obligatory prayers, it is not permissible.
Tayammum for an obligatory prayer is not valid before its time has begun.
It is valid for non-timed voluntary prayers at all times except the disliked times.
One who performs Tayammum for a supererogatory prayer cannot perform an obligatory prayer with it according to the prevalent opinion.
They can perform what they intended of the supererogatory.
The time for a missed prayer is when it is remembered.
They perform Tayammum for it when they remember.
