Monthly Availability (Last 12 Months)

This requires disabling the HTMLResourceSanitizationEnabled setting on modern versions of the platform.  This can be done in the Advanced Configuration area of the web.  Please review the possible risks is making this change.

I tried to copy and paste this in a custom html but I only see the code and not the widget when I submit in SW

Last 30 days or the previous month?  They are two different things and I want to make sure I'm producing the correct information.

How can i get the report for Pervious month only

if you want to remove the date limitations, then you should remove the WHERE (YEARDIFF(DATETIME,(GETUTCDATE()))=0) line.  That will give you "forever" but just be aware that the number of entries might get big and your query might timeout.