Can I wear apple watch as a necklace

You could but as mentioned, you would lose most functionality. If one of the reasons you were interested in the watch was for fitness tracking you won’t have that while wearing it around your neck. You would constantly have to put in the passcode (but it would automatically lock again if it’s not in constant contact with your skin. In that case, if you’re not concerned about or interested in any of the smart watch features you would be better off just finding a watch pendant necklace. I know you said you find it hard to wear a watch but curious is it just a comfort thing (like not being used to wearing anything on your wrist) or do you have issues that happen like skin irritation?

You won't be able to use the heart rate functions. And, I suspect that any activity data will be inaccurate a lot of data comes from arm swings.

You would have to set it up with a passcode PIN.

No PIN code, so no Apple Pay.

Cannot unlock your Mac

Cannot unlock your iPhone if you are wearing a mask.

You cannot use your Apple Watch to authorize Mac activities where an admin is needed.

There are other things, I'm sure.

I don't see why not, but some of the features might not work if they rely upon constant contact with your arm skin or are otherwise designed with being worn on an arm.

Bottom line? You can wear the watch as a necklace BUT all it will be useful for is a clock, nothing else.