1. all your html must place after <body>, instead of <head> ~ </head>
2. the blogger data tag ‘data:post.firstImageUrl’ only works between POST AREA, will not work in whole blog. You could use another data tag ‘data:blog.postImageUrl‘, it will work in any location in whole blog
You will find the options for post image as feature image in above < head > tag. It is easy to handle and you will get the idea to make your work more better . Hope you have aware of the ayurvedic treatments in Kerala started with best facilities. Through the Ayurveda treatments you will get a different feeling in your life.