Why my iPad Air 2 doesn't show the calling app as well the weather app and few more

An iPad is not an iPhone. It cannot make calls. There is no Phone app on iPad. It can do FaceTime, which allows it to call Apple devices.

The iPad does not include a Weather app. Nor does it include a Calculator app.

If your iPad model is an iPad Air 2, it can run iPadOS 14.

iPadOS 14 has a working weather widget that you can add and use use, in place of a built-in app.

Add widgets to the iPad Home Screen - Apple Support

The SIM card, which is optional, is used for cellular data. This allows internet access when a Wi-Fi signal is not available. Again, your iPad is not a cellular telephone.