After uploading a horse novice status can not be changed to non novice and vice versa for obvious reasons. If you upload a horse and don't make it a novice you will have to delete the horse and re-upload it. After deletes close we will need to change this for you and provided the horse has not run that can be done.

Juveniles must be uploaded as novices.

For new trainers a novice can not run in any non novice races, only in novice races and non graded handicaps. A novice will remain that for the rest of the season so ensure you have made the correct selection

Non novice horses can not run in novice races.

Before the season starts can I edit a horse from novice to not novice or does it actually have to be deleted first?

You need to delete it first

Can I just clarify what age the horse needs to be to be a non novice or a novice please?
Thanks

Its up to you you just have to declare what they are at the start of the season, but if you possibly want to bring a horse back for the following season it can no longer be a novice and must logically be 1 year older so think about that if you aim to have returning horses

Juveniles must be 4