1) We are entitled to get 12 holidays every year or per year or each year?
Every/per/each are all OK. However, when you say "12 holidays", do you mean 12 separate days or 12 periods of absence from work. If the former then you need "We are entitled to 12 days' holiday every year". If the latter "We are entitled to 12 holidays every year", but that sentence doesn't clarify how long each holiday might be.
Which one is correct?
2) Can we take off/holiday on Eid/Christmas? ---- is the sentence correct?
Can we take time off at Eid/Christmas?
Can we take holiday at Eid/Christmas?