Apple phone has been reset. How do i achieve getting all my photos, calendar, any important thing that was on my phone backed up into icloud?

Usually, after a factory reset, it should give you the option to "Restore from iCloud Backup". That's the best option.

If you didn't see it or for some reason it didn't offer this, then the next easiest way is to sign back in to all apps and services that used your AppleID.

If you are already on the "Home Page" of the iPhone, then make sure you go into settings...

Find iCloud--make sure you're signed in to all previous services and they are switched on.

Find Mail--make sure all your accounts are there and you are signed in, or even reenter your passwords so they reactivate (if none of your accounts are there, you will need to re-add them, sign in and wait while all the data is downloaded to your device. (If you don't remember your passwords, there is no harm in hitting "forgot my password" to change it, so that you can change it, write it down/save it, and remember it)

Lastly, scroll though ALL of your Settings page and double check that you are signed in to any app or service that you previously had. Also, redownload all apps, from the App Store, that you needed or wanted on your iPhone.

That depends on how you used iCloud. iCloud+ has 2 independent functions. iCloud backups, and iCloud sync. It’s confusing because they both have the same name prefix. But they have no connection with each other. Go to Settings/[your name]/iCloud. You will see a bunch of switches (with iOS 16 also tap Show All). When you turn on a switch that data type will sync to iCloud. If you do this on multiple devices that share an Apple ID the selected data will sync to all of those devices. 

You can also turn on iCloud Backups. This will back up your phone every night if the phone is plugged in, connected to Wi-Fi and locked.

But note that anything that you sync by the first method will be excluded from the iCloud backups.