What is a proper adjective?

Proper nouns are usually not used with articles. For example: I live in Delhi, He works at Google. However, exceptions apply in cases when the article is a part of the name.

For instance:

The University of Delhi has many colleges affiliated to it.

 The Times of India is a prominent English-language newspaper in India.

Proper nouns are usually not used with articles. For example: I live in Delhi, He works at Google. However, exceptions apply in cases when the article is a part of the name.

For instance:

The University of Delhi has many colleges affiliated to it.

 The Times of India is a prominent English-language newspaper in India.

Yes, certain proper nouns are plural like the Himalayas, the Ahujas. In these cases, no apostrophe is used.

Example:

The Smiths moved in our block yesterday. (Family or Dynasty names)

The Lord of the Rings books are a good read. (Series Titles)

This song is sung by the Beatles. (Musical/Performance group)

Yes, certain proper nouns are plural like the Himalayas, the Ahujas. In these cases, no apostrophe is used.

Example:

The Smiths moved in our block yesterday. (Family or Dynasty names)

The Lord of the Rings books are a good read. (Series Titles)

This song is sung by the Beatles. (Musical/Performance group)

No, seasons are not capitalized because they are common nouns.

For example: I love spring because of the flowers.

My exams are in winters.

However, in some cases, the seasons can be capitalized only if they a part of a formal name.

Example:

“Summer of '69'” is her favourite song.

I participated in Spring Festival Committee.