What should the worshipper do if he inadvertently misses some of the takbeerat of the funeral prayer, such as the second or third, and merely raises his hands, then invokes blessings upon the Prophet (peace be upon him)?

The four takbirat (Allahu Akbar) in the funeral prayer are pillars, and the prayer is not valid without them. Each takbirah is considered equivalent to a rak'ah. So, if someone forgets the second takbirah and only remembers it at the third, they should consider the third as the second, send blessings upon the Prophet (peace be upon him), then complete their prayer with the Imam. When the Imam says the taslim (definition) (final salutation), they should make up one takbirah. If someone who was not a latecomer intentionally omits a takbirah, their prayer is invalidated. If they omit it due to forgetfulness, they should say it as long as the interruption is not prolonged, and their prayer will be valid.