@pitaj Thank you. Issue was with the condition. I have used condition as shown below which solved the problem.

post.posts[0].tid === 1090

Thank you all for the suggestions. I tried @PitaJ `s solution. This is what I have done:

In library.js in my custom theme, I added:

benchpress.registerHelper('isTaskList', function (post) {
        return post.tid === 1090;
});

In lib/persona.js in my custom theme, in the $(document).ready event, i added:

templates.registerHelper('isTaskList', function (post) {
        return post.tid === 1090;
});

And then in the templates/partials/topic/post.tpl, I have used:

<!-- IF function.isTaskList -->

as the condition

The condition is working as expected when the page is initially loaded for the posts that are loaded/displayed initially, however when I scroll down and when the further posts are getting loaded/displayed at the bottom of the page, the condition is not taking into effect. Could you please advise if something is missing?

@julian Thank you for replying. I am thinking of a small hack in that case. Let me know if this will work. What if I create a custom route and use a modified version of the original topic.tpl as its template?

var controllers = require('./lib/controllers'),
plugin = {};

plugin.init = function(params, callback) {
	var router = params.router;
	var middleware = params.middleware;

  // Define the function that renders the custom route.
	function render(req, res, next) {

		// Get data object corresponding to the specific topic. The topic ID is fixed.
		var data;

		// This is the path to your template without the .tpl, relative to the templates directory in plugin.json
		var template = 'my-custom-page'

		// Send the page to the user.
		res.render(template, data);
	}

	// This actually creates the routes, you need two routes for every page.
	// The first parameter is the actual path to your page.
	router.get('/my-custom-page', middleware.buildHeader, render);
	router.get('/api/my-custom-page', render);
  
	callback();
};

module.exports = plugin;

'data' needs to be filled with information about a specific topic. If this is possible, then how can I get the data object corresponding to a particular topic in the render function? Is there some function that can take a topic id as input and just return 'data'?

Is it possible to have a custom template for a particular topic (identified by a topic id)? Something like topic_tid.tpl somewhere in a plugin or theme? My intention is to be able to theme a specific topic and leave the remaining use the default topic template.

This app helps a lot. It works well with OneSignal notifications as well. But one doubt. When sending notification from OneSignal, when user clicks on the notification in mobile, can they be redirected to a page in the app?

@yariplus Thank you. This helps a lot.