The following method is used to detect child component Input() changes in Angular using ngOnChanges()

import { Component, Input, OnChanges, SimpleChanges, ChangeDetectionStrategy } from '@angular/core';
import { User } from './user.model';

export class SelectedUserComponent implements OnChanges {
    @Input() user: User;

    ngOnChanges(changes: SimpleChanges) {
        console.log(changes);
    }
}

To remove the old data from the search engine you need to add 301 redirects to your old pages.
The below method is used to redirect your old page to a new page using 301 redirects in Angular Universal. This is by default code in server.ts file

// All regular routes use the Universal engine
  server.get('*', (req, res) => {
      res.render(indexHtml, { req, providers: [{ provide: APP_BASE_HREF, useValue: req.baseUrl }] });
  });

All routes come here then the express server(SSR) renders the front-end angular HTML files. So before sending any response to the browser we can send the 301 status code.
You can add some conditions like below

// All regular routes use the Universal engine
  server.get('*', (req, res) => {
    if (index == req.originalUrl)
      res.redirect(301, 'https://www.samprix.com');
    else
      res.render(indexHtml, { req, providers: [{ provide: APP_BASE_HREF, useValue: req.baseUrl }] });
  });

Sample environment variables for development & production environment.ts

export const environment = {
    env: 'Dev'
};

environment.prod.ts

export const environment = {
    env: 'Prod'
};

In the above code using the window object like below:
environment.ts

export const environment = {
    env: window['env'] || 'Dev'
};

environment.prod.ts

export const environment = {
    env: window['env'] || 'Prod'
};

Create a .js file in the root directory and add it to index.html file as a script

<script src="./config.js"></script>

In the config.js file, you can update the environment values without rebuilding your application like below:

window['env'] = 'Uat';