1. It was great fun last weekend for you to visit our nursing home.

2. Your visiting our nursing home was great fun last weekend.

3. The visit was great fun last weekend.

4. Visiting our nursing home was great fun last weekend.

(Are they all grammatical and interchangeable? Or which ones are acceptable grammatically?)

All are grammatically correct.

#s 1 and 3 are probably most likely to be used in normal speech.

#s 2 and 4 are slightly awkward even though they're grammatically fine.

they are all grammatcal and interchangeable. 1 $ 2 the best

All of the provided sentences are grammatically acceptable, but they have slightly different structures and meanings. Let's analyze each sentence:

1. "It was great fun last weekend for you to visit our nursing home."
This sentence places emphasis on the fact that the visit to the nursing home was enjoyable for the person being addressed. The subject "it" refers to the general experience of the visit.

2. "Your visiting our nursing home was great fun last weekend."
This sentence highlights the specific action of the person being addressed visiting the nursing home. The possessive pronoun "your" indicates that the visit was performed by the person being addressed.

3. "The visit was great fun last weekend."
This sentence focuses on the visit itself rather than the person who carried it out. It is a straightforward statement about the enjoyable nature of the visit.

4. "Visiting our nursing home was great fun last weekend."
This sentence emphasizes the activity of visiting the nursing home in general, without specifying who performed the visit. It is a more general statement compared to sentence (2).

While all the sentences are grammatically correct, they serve different purposes and convey slightly different meanings. Therefore, their interchangeability depends on the intended emphasis or focus of the speaker or writer.