bluetooth is not available after restart(iTunes update), keyboard and mouse does not work

How to reset the System Management Controller (SMC) on your Mac

However, three to four devices is a practical limit, depending on the types of devices used. Some devices require more Bluetooth data, so they're more demanding than other devices. Data-intensive devices might reduce the total number of devices that can be active at the same time.

If a Bluetooth device doesn't appear in Bluetooth preferences, or if it becomes slow to connect or doesn't perform reliably, try turning off devices you aren't using or unpair them from your Mac.

Using a Bluetooth mouse, keyboard, or trackpad with your Mac

Start up in safe mode

To start up in safe mode:

1. Start or restart your Mac, then immediately press and hold the Shift key. The Apple logo appears on your display. If you don't see the Apple logo, learn what to do.
2. Release the Shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder.

To leave safe mode, restart your Mac without pressing any keys during startup.

If an issue doesn't happen in safe mode

If an issue doesn't happen when your Mac is started in safe mode, try restarting without pressing any keys.

• If the issue comes back, you might have incompatible login items.
• If the issue doesn't come back, it was probably caused by a cache or directory issue with your startup disk, which safe mode fixed.

Use safe mode to isolate issues with your Mac