Just having a cursory glance at the website in question, most (if not all of the stories) look rather conspiratorial. For example one of the top stories suggests India is a victim of "Freemason Orders," the British and the Church disconnecting it from its awareness of Space-Time, which I hope I needn't explain the absurdity of that.

Additionally there's another article which blames Darwin for the Bengal Famine and suggests he supported Eugenics despite his noted apprehension regarding the matter.

Yet another article suggests (it doesn't outright say it but the implication is there) some sort of "deep state" existing in the United States were responsible for the assassination of John F. Kennedy and that Donald Trump could be next, which is again ludicrous.

I can't claim to be an expert on Israel, so I hope someone else can provide an answer regarding the activities of Mossad and Shin Bet during the 50's and 60's. In Lieu of a better answer, I wouldn't trust this website.

This is not a credible site. It really isn't.

1. does this actually qualify as an assassination attempt ?

No. "Aggressive maneuvers" against another plane are not grounds for calling it an assassination attempt. If they had fired on the plane, you could perhaps say that...but they'd have almost certainly succeeded if they'd attempted an assassination.

And this is a strange story. Nehru and Israel actually worked together in 1962, and Israel shipped weapons to India.

2. What could Israel possibly gain from such a thing at the time ?

The story as recorded by Israel is that they saw a UN plane one mile inside Israeli territory, intercepted it, and escorted it back to the border. Nehru said he considered the matter closed when he mentioned it to the Indian parliament, and it was considered a non-incident. See for example here.

Almost no one I've seen puts much importance to this, and the website is clearly just being clickbait.