Q1 Yes they can remove them as they were unapproved, they don’t need your approval (common property) but they cannot bill you for the work.
Q2 Just needs an ordinary motion to be approved to remove them.
Q3 Yes the EC (or the OC) can approve the repair (so long as the cost is within their limits).
IMHO the reason they don’t need a special resolution to make the changes is because the installation of the pavers is unapproved and they are just doing a repair to return the Common Property back to it’s original state.
Common property belongs to everyone and if they have the votes they can do what they like UNLESS you have been given exclusive use of said common property and that fact is recorded in the bylaws.