I think not writing inside the lines is a red herring. Can they do that if asked?
Id say a child of 6-7 but have written this in a rush or through play. OR a 4 year old who has taken great care but just has poor pencil control.
It's odd in that there are finger spaces and full stops but then other elements seem very young, such as upper and lower case and then putting the full stop in a random place.
Another possibility is a 4 year old who actually had some help with this.