Is it possible for oranges to become intelligent life while still retaining some of their essential qualities such as skin that can neatly be peeled off and reproduction through seeds and growth off of a tree?
To be successful, the orange must be eaten in such a way that the seeds are not destroyed, but dispersed.
Imagine a fruit which encountered difficulty finding something to eat it. Maybe hungry things are few and far between. A mobile fruit could wander away from the tree which would improve its chances of finding something to eat it. Selective pressure would favor a fruit which could organize its wanderings to better fulfill its purpose of finding something hungry. Fruits which could overcome obstacles and solve problems encountered on the way would also be selected for.
When these intelligent oranges are eaten and the seeds grow, the tree is just a tree. It is intelligence on the part of the fruit that is selected for. It would be a very single-minded and purposeful intelligence, and not like the utilitarian omnivorous intelligence that humans have.
The fruit itself - no. Oranges are not organisms per se; they are propagation & dispersal containers for the next generation of organisms - fruit trees.
For a start; orange trees are actually more successful if the fruit gets eaten. This is why the tree invests so much energy into the production of fruit; so that animals eat it, consume the seeds, then go somewhere else and defecate out seeds with their other waste, providing the seed with fertiliser and a new location in which to grow. In that respect, evolution is going to work against the orange at every turn because the longer it 'survives', the less chance there is for the orange tree to create successful offspring. This is why fruits also change to bright colours when ripe; it's because from an evolutionary perspective, the tree wants them to be seen, and eaten.
Of course, if the orange develops intelligence and decides it doesn't want to be eaten, well that's a complication that the tree could do without, and it's bad news for them both - the tree doesn't get its seeds dispersed, and the orange starts to die the instant it separates from the tree by being picked. It no longer has any nutrients other than the ones in itself, and when it dies, it can't replicate itself, only another tree. So even IF the fruit was left in a condition where intelligence would prolong its existence, it has no way to pass on those genes other than to grow another tree, and it's competing against fruit that is already consumed as quickly as possible.
Also, while intelligence isn't knowledge, its the cumulative body of knowledge that we share with the next generation, upon which they build, that provides the foundation for the body of patterns that we work with to understand and recognise newer, more complex patterns in our turn. It's that ability to identify and recognise complex patterns that is our intelligence.
If you were to take a child (please don't do this, BTW) and at the moment of birth place it in an sensory deprivation chamber for the next 20 years, the child may have the capacity for intelligence, but that capacity has not been honed and built upon through observation, experimentation and the learnings of those who have also tried similar things.
Your oranges will be in a similar situation - by the time new ones are born, their parents are long dead so even if they had a way to communicate (which they don't), each generation is separated by the years involved in the growing of the next tree.
For the sake of argument however, what if instead of intelligent fruit, we went with intelligent trees that use fruit as their dispersal and propagation model?
This is certainly possible - they have an opportunity to observe the world around them, but they need much more than that in order to develop intelligence - they need memory. Without the ability to remember a pattern, they have no way of recognising it in the future.
In animals, that capacity to remember is laid down in the brain. In humans, we invest around 20 to 25% of our energy intake into our brains because of the massive benefit we get for that cost.
Trees on the other hand have been surviving, and thriving, for over a billion years without the need for that energy investment. Add to that, even if a tree could recognise a pattern that indicated danger, exactly what could it do about it? So instead of investing in intelligence, these trees invest energy in their propagation system - fruit. It's a successful strategy, and the only way that it's likely to change is to either become more efficient or for there to be a change (like complete absence of animals) in the environment that requires a different approach for success.
That said, neither of those scenarios will demand the heavy energy investment needed for memory and intelligence.