Which amongst the following is another name for the 'Buddha'?

Tathagatha

The correct answer is Option (4) → Tathagatha

Tathagatha is another name for the 'Buddha'.

This is an excerpt from the Mahaparinibbana Sutta, part of the Sutta Pitaka:

As the Buddha lay dying, Ananda asked him: “What are we to do Lord, with the remains of the Tathagata (another name for the Buddha)?”

The Buddha replied: “Hinder not yourselves Ananda by honouring the remains of the Tathagata. Be zealous, be intent on your own good.”

But when pressed further, the Buddha said: “At the four crossroads they should erect a thupa (Pali for stupa) to the Tathagata. And whosoever shall there place garlands or perfume … or make a salutation there, or become in its presence calm of heart, that shall long be to them for a profit and joy.”