When you want to keep the fragrance good for longer than a few weeks an antioxidant is necessary. When you use a lot of easily oxidised products like citrus oils it is always needed. Note that an antioxidant is added to most essential oils and many aromachemicals already. BHT is the most common one, though tocopherol is also rather popular.
An UV filter is needed when you want to keep your perfume good for a longer time and be able to have it in the sun. When you make a commercial fragrance you don't know how people store their fragrance, so therefor it is safer to add an UV filter. Benzophenone-2 is the most common, I think.
Octylacrylamide copolymer is an viscosity enhancer or film former I think. I suppose it is not very common in fragrances, might act like a fixative.
butylphenyl methylpropional is Lilial, one of the 26 allergens we have to put on the label in the EU.