do all ipads have sim slot

Only WiFi+Cellular models of iPad have cellular capabilities - this including the GPS functions of which you enquired in your earlier post.

WiFi Only models of iPad do not have any Cellular hardware components - nor do WiFi Only models have any GPS capabilities.

No, only those with Cellular connection have af SIM slot. You can read more about it here:

https://www.phonearena.com/news/ipad-wifi-vs-cellular_id127422