I suppose part of the question is how liberal you want to be in using the term “blazer” to describe a jacket with a flat collar and notched lapel which uses a buttoned closure. To me, Jenni NZ, none of your gorgeous jackets are “blazers” since they all offer interesting and unique interpretations of the traditional blazer design. Number 6 is the closest, but since the collar and lapel are styled to be worn forward instead of turned back, it pushes the boundaries of Blazerdom for me.
But remember I’m an oldie who was raised in an era when it was standard attire for men to wear suits, hats, and wool topcoats to work. A blazer was considered a less formal jacket since it could be paired with non-matching flannel or twill trousers and was an alternative to a suit for more casual daytime wear. Sports jackets, though, were a totally different jacket; they were usually made of sturdier material like tweed or twill and often referenced their country/hunting heritage in having belts, tabs, and leather patches added. My dad would never have worn his Norfolk sports jacket to an evening event—it would have been like wearing sneakers to the opera. If it was an evening event, he wore a suit—or a dinner jacket. And this man was just a high school teacher!
It’s also worth noting that to those of oldies raised in countries which were part of the former British Empire, blazers have both military and upper-class connotations. A blazer was a component of the British naval dress uniform ( sometimes referred to as a “reefer”), as well as the preferred attire for British rowing teams and school uniforms. The upper pocket often sported a house crest, the buttons had special insignias, and the color of the jacket and piping was specific to the school, group, or club. The color combinations for clubs and schools were often quite loud, while the military versions were more subdued. Blazers were quite often worn with regimental and club ties. A woman’s version of the blazer was normally fitted, tailored, and hip length.
So, given all my blazer baggage, it’s hard for me to label any of your jackets as a blazer. Number 3, though, is interesting. Replace the collar with a flat collar, add a proper lapel, and remove a couple of buttons—and, voila, you’d have a blazer which resembles some I’ve seen worn by rowing teams. The back pocket might be even be viewed as a useful design feature by those rowers!