Can you Apply for an officer after leaving college isntead of 6th form and can you just join the army normally and then train to become an officer by any chance?

Some Branches will require you to have a Degree before joining. You would be able to join those that don't after college yes.

You can join as a non commissioned rank but you will have to be selected by your Seniors for selection for a commission and will then require to meet all aspects that someone joining straight as an officer would require. e,g Interviews. You will then have to join Sandhurst (If army) and train alongside people that have joined directly as officers aswell as others who have already been enlisted. Depending on your experience your time there may not be aslong as a normal entries.