How to add the 3 most recent posts to front page

Try using RSS-digest. You can find it at:

https://www.bigbold.com/rssdigest/

Example number 2 should help. Be sure to put the wp-blog-header.php call at the very top of index.php and then put your Loop call where you wish to display those recent posts.

https://codex.www.ads-software.com/index.php?title=User:Schulte/Display_WordPress_Posts_on_Non-WordPress_Site&action=submit

Get CG-FeedReader is an easy way and what I use. You can display it any number of ways. I just have it display the title of the posts in an in-line list.
https://www.billhayes.us/

Edit: I posted the wrong plugin name, fixed now.

https://www.transycan.net/blogtest/2005/07/05/integrate/
Scenario #1