Is the prayer valid if the worshipper makes a mistake in the number of rak'ahs and forgets the prostrations of forgetfulness (sujud al-sahw) before and after the taslim, and then gets up from the prayer?

The question is general, but if the increase in the number of rak'ahs (units of prayer) was due to forgetfulness, then the prayer is valid, and the Sunnah is to perform the two prostrations of forgetfulness (sujud al-sahw). However, if the error was a decrease in the number of rak'ahs, meaning a rak'ah was inadvertently omitted and not performed, then the prayer is not valid and must be repeated, because the prostrations of forgetfulness do not compensate for the omission of a pillar (of prayer).