2:21
Allah created the mankind; they should worship Him.
Contradiction: 3:97, 35:15 say Allah does not need mankind and the jinns; He is free of all want.
This is not a contradiction. Existence of Allah is independent of human and jinn, a Muslim is free not to pray, Allah is not dependent upon his praying. It is Muslim who shpould pray if he wants Jannah.
Contradiction in Quran should focus upon opposite message in Meccan and Madina suras. Just taking lines, without going through tafsir, makes the attemt laughable. Personally I find medssage of Quran pretty consistent.
+1. Which is why I found Atheist/Christian attempts to "refute" the Qur'an so hard to follow, they didn't read carefully enough to see what they were saying was weak

. If you're going to "refute" something, you should do so on strength, and not flimsiness

.