Do I have to purchase a genuine copy of Microsoft Office for everyday use?

You can get a compatible alternative or open source program, but they do not operate the same and take more time to achieve the same results. If you have a high everyday volume then the original is best. If it is for occasional use with flexible due date then the others will eventually get the job done. Basically you need to decide what is more important, time or price.

You can if you want to get the maximum results out of the original software, or you can get the non official one just to get the job done. But it wouldn't be the best solution. 

No you dont have to purchase genuine copy every day