Understanding from vs since for time
Q1. I have known her ___ 2015
SINCE is used with perfect tenses to mark a starting point. 2015 was the beginning. Friendship persists.
Q2. The shop is open ___ 9 AM ___ 6 PM
FROM...TO indicates a range. Nine to six is the schedule. Commerce occurs within these bounds.
Q3. ___ childhood, he has loved music
SINCE marks the starting point continuing to now. Childhood was the origin. Music remains.
Q4. I work Monday ___ Friday
FROM is implied before Monday. TO Friday completes the range. The work week is defined.
Q5. Which sentence is correct?
SINCE with perfect tense is correct. FROM would require a different construction. Residence continues.