Who approves the feature and bug code reviews in Bitcoin? I see a list of Bitcoin feature and pull requests here. How do all million plus users agree to these feature/bug requests? Do all users of Bitcoin have to approve them, or who represents them in approving these code requests?
Where can I access the original, Satoshi written Bitcoin code?
How do all million plus users agree to these feature/bug requests?

Mostly by deciding whether to continue using Bitcoin-core or switch to one of the many other existing implementations of a Bitcoin wallet.
Those who are particularly competent to assess the changes are probably also, in many cases, competent to fork the code base and not introduce changes they object to. If others share their view of the changes, this might be viable. Certainly Bitcoin core has been forked many times in the past.

Do all users of Bitcoin [core] have to approve them

They mostly get to vote with their downloads.

Related questions

Where can I access the original, Satoshi written Bitcoin code?
Original default bitcoin script
Do &quot;the official bitcoin developers&quot; control Bitcoin?
Is the Bitcoin Core software managed by a central authority?

Other relevant sources of information

https://satoshi.nakamotoinstitute.org/code/