can we install multiple application in single script. if Yes, can you please share the script ?
Yes. A super easy way to do this is to use package management tools such as https://chocolatey.org/ .
You can create simple one line scripts then to install many applications, including your own custom applications.
That depends on the application. Some applications expect a reboot after their installation and some other applications check if there’s been an installation before with a reboot pending.
There are thousands of examples for scripts in the internet. Please use your favorite search engine to find something suitable.
You may take a look at PSAppDeployToolkit