How to make Siri available when I open my MacBook? When I open my laptop, I can click on Chrome exe and launch the browser.

I know I can ask Siri to open Chrome, but I have to click to the Siri icon (or the keyboard shortcut) and then ask her to, which - well - is more work than just clicking Chrome. It will open Chrome and terminate.

Can I make Siri be available at startup? Open Chrome when she asked to and then terminate.
I think you can't.
But, if what you want is just to open Chrome at login, just left-clic the Chrome icon in the dock, then Options > open at login