Check the steps to insert sim:-
A video for your reference:
You can find complete specifications here: Google Pixel 3
There are two ways to take screen shot in upcoming android P 9.0 devices including Google Pixel 3 and Pixel 3 XL.
Press and hold the power button and volume down button at same time to take screenshot
In upcoming android P 9.0 device (Pixel 3 & Pixel 3 XL), you will capture screenshot using power button menu.
Open page you want to take screenshot > Long press power button > Screenshot
The launch of Google Pixel 3 Mini is rumored and it might launch in Q4 2018.