Correct sentence:
The game of football is not all that complicated.

not all that [idiom]

• English Meaning: not very, or not really.

• Bangla Meaning: তেমন নয়; খুব বেশি নয়; আসলে নয়।

Examples:

• It isn’t all that cheap.

• The game of football is not all that complicated.

• I'm not all that excited about going camping.

Option Analysis:

খ) The game of football is not so that complicated.

•   ভুল। "So that" একটি conjunction যা উদ্দেশ্য/ফলাফল বোঝায় (e.g., She spoke loudly so that everyone could hear.)।

• এখানে adjective-এর আগে ব্যবহার করা যায় না।

গ) The game of football is not as that complicated.

•   ভুল। "As that" combination সঠিক নয়। Comparison করার সময় ব্যবহার হয় as...as structure (e.g., not as complicated as).

ঘ) The game of football is not all so complicated.

•   ভুল। "All so" standard English-এ ব্যবহৃত হয় না।

 Source: Cambridge Dictionary