Step 1: Understanding the Question:
We must identify the segment containing a grammatical error or an incorrect prepositional idiom.
Step 2: Detailed Explanation:
Let us analyze part (2): "put up in a hotel".
The sentence uses the phrasal verb "put up in" to describe staying somewhere.
When we talk about staying temporarily at a place as a guest, the correct idiomatic phrasal verb in English is "put up at" or simply "stay at".
For example: "We put up at a guest house for the night," or "I stayed at a hotel."
Using the preposition "in" with "put up" is grammatically incorrect in standard English for describing accommodation, although it is a very common colloquial Indianism.
Therefore, the preposition "in" should be replaced with "at".
Additionally, in part (3), the phrase "boarding and lodging" is commonly used in Indian English, though traditional British standard prefers "board and lodging".
However, "put up in" is definitively and universally incorrect as a prepositional phrase in this context.
The correct phrasing is: "I could not put up at a hotel..."
Hence, the primary grammatical error lies in part (2).