The PAN card is an identity document. Its valid even if you did not file income tax or used for sometime. It can be used to prove the date of birth.
I wouldn't recommend it, especially with the discussions about banning them in the whole of India:
The government, in an ordinance piloted by the Health Ministry, is planning to ban e-cigarettes and vaping devices. A cabinet clearance and subsequent notification would put the ban into effect. The ordinance banning all Electronic Nicotine Delivery System (...
I definitely recommend mentioning the visa. After all, you don’t want to not mention it and then be refused if they uncover this information.
What I suggest to do is to:
State correctly that you have been issued a visa before, and been to India.
State "Yes. See attachment 1" in "Have you ever visited India?" question.
Add a document titled "...
Plans change all the time. Not using a Visa is not at all an issue.
A personal experience. I applied for Malaysian visa, got that. But I couldn't use that visa, as my plans got changed. When I applied second time, they didn't even asked any questions. Your visa is here.
Don't give explanation on why didn't you use previous visa, unless it is asked (most ...