If I want to be a photographer how many A.levels and O.levels most of colleges take
You can no longer do o levels, they do not exist. O levels are considered to be GCSEs and after completing year 11 you either do A levels or a level 3 BTEC.
Are you thinking of doing 3 a levels or a btec? Both choices could allow you to become a photographer. It's possible to do a BTEC in photography with the exam board edxcel (link below) However, you can also do a levels, whereby you do one a level that's photography and then two other optional a levels of your choice. Have a look at the links below, especially the UCAS page. It shows you different qualification pathways you can take in becoming a photographer. A level 3 btec is equivalent to 3 a levels by the way.