I change my page title and meta desc, and also change indexability status to index. Should I wait till google crawl again or change by itself? or I can notify google that I change something and please crawl again sooner?
Log in to Google Search Console
Add and verify your website, if you haven't already.
Paste the URL of the page you want updated into the search bar at the top.
Click "Request Indexing"
This asks Google to crawl your page again sooner, rather than waiting until the next automatic crawl.
It's my understanding that the more regularly you write and update content on your site, the more often Google will review your site for changes. Thus if you update your content daily, Google will revisit your site more often than if you only update your content weekly or monthly.
In my own testing I have found where I publish new content on a weekly basis, that I need to tell Google about new pages if I'm not willing to wait a few days for it to show up on Google.
Remember, you can use site:example.com, click on Tools and change "Anytime" to reflect a time period you wish to search. You can get a rough idea from this how long it takes Google to find new content on your site. And, just because you change something doesn't mean that Google will necessarily re-index it.