# [Python 3], <s>105</s> 102 bytes

3 bytes thanks to Mr. Xcoder.

<!-- language-all: lang-python -->

    def f(a):l=len(a)-1;r=range(l+1);return[[a[i][j]+a[l-j][i]+a[l-i][l-j]+a[j][l-i]for j in r]for i in r]

[Try it online!][TIO-jcn856dl]

[Python 3]: https://docs.python.org/3/
[TIO-jcn856dl]: https://tio.run/##bU9BCoMwELz3FXs0mIJrrLUVXxJyEKptgkQJ9tDXp5sYoUghh5nZmZ3N8llfsxXeP4YRxqxn96mbBkvgjK3rXG@fQzblyFo3rG9npeylVtKovJfT2SgiEZEWKGGjIh1nBwa0BReh3qBfnLZrNmZSolKMnX44B6E4yJJDdRiRdOHQhKnggGXCNQd6WBwXVVG/0qhKthDBEBVJIC5ilCitxmQp/6zayrEgFNzYcLglO6H9ps2Ee2coK4vtiOhOP8MYJmsdmvwX "Python 3 – Try It Online"