When you hover on "On" it gives you "Sur".
Cause it means On in the 3d space, les cadeaux sont sur la table, the gifts are on the table
Why not 'en vendredi'?
As evidenced by the correct answer here, French and English are different when it comes to dates.
French use "en" for months and years, not for days.
Yes, because "on" may mean "sur" in many circumstances.
"le chat est sur la table" = the cat is on the table.