Hi, I will answer your questions directly in english because most forumers don't understand nor read italian.
In any case speaking of acquisition cones, a cone has a circular section that means that the horizontal and vertical diameters coincide.
No, the speed of the torpedo is fixed at launch time. If you fire a passive torpedo at 35 knots and it acquires a target it will continue at the same speed and will not accelerate.
The torpedo doesn't automatically change passive and active modes.
Good hunting :|\
Ps: stop playing 688i h/k and buy Dangerous Waters