QUESTION: Fix punctuation: Opera 35 Final is available as a download on the official Opera website as well where new and existing users can download the release from
ANS: Opera 35 Final is available as a download on the official Opera website as well where new and existing users can download the release from.

QUESTION: Fix punctuation: The stones served many functions
ANS: The stones served many functions.

QUESTION: Fix punctuation: It is located just a few meters from Las Ramblas Sant Jaume square and metro station the Iglesia de Sant Felip Neri and the Catedral of Barcelona
ANS: It is located just a few meters from Las Ramblas, Sant Jaume square (and metro station), the Iglesia de Sant Felip Neri and the Catedral of Barcelona.

QUESTION: Fix punctuation: Microliths are small arrowheads weighing a few grammes and in this case they functioned as points on the arrows that brought down the large animal
ANS:
Microliths are small arrowheads weighing a few grammes, and in this case they functioned as points on the arrows that brought down the large animal.