The rules are there to ensure that it is fair to everyone who applies for a particular job.
Ensure the length of your CV is appropriate and that you follow any instructions they provide.
Too short and you’re not giving me what I need to make a decision. Too long and you’re making me hunt for the information I need.
Both of these are frustrating, and when you have 500 CVs to look through it can easily make me give up.
Unless this is your first ever job then 1 page is too short. Aiming for 2-3 pages is perfect.
A CV with 4 pages in it is getting a little long. 5 or more pages are just mostly waffle and leaving me to search for what I want.
I’m sorry but I really don’t care about what you did 10 years ago. I’m a radically different person from who I was 10 years ago and I am sure the same is true for you!
As well as your CV length, did the job advert mention about a cover letter or a portfolio. Did it mention that you needed to send it to a certain email address with a specific subject name? If there is this request, you should be following the exact instructions provided or your CV won’t be put forward.