Analysis of 7 scenarios for conveyor belt models

The analysis of 7 scenarios for the conveyor belt model is as follows:
Horizontal conveyor belt. The slider keeps accelerating, with a force of f=mg, accelerating first and then moving at a constant speed, and the force becomes f=0.
Horizontal conveyor belt, with the slider starting to slow down at a certain speed v0. The force is f=mg, slow down first and then move at a constant speed, and the force is still f=mg.
Horizontal conveyor belt, the slider slows down first, then accelerates to the right, and finally reaches the right end at a constant speed of v. When decelerating and accelerating in reverse, the force is f=mg, and the direction is always right. When moving at a constant speed, the force is f=0.
Tilt the conveyor belt and the slider keeps accelerating. Friction force f=mgcos θ， Accelerate first and then move at a constant speed, subject to frictional force f=mgsin θ。
Tilt the conveyor belt and accelerate the slider with acceleration a1 first, then with acceleration a2. Friction force f=mgcos θ， Accelerate first and then maintain a constant speed, with frictional force f=mgcos θ， After being subjected to reverse frictional force, f=mgcos θ。
Tilt the conveyor belt, with the slider constantly moving at a constant speed of v0. Friction force f=mgsin θ。
Tilt the conveyor belt, with the slider slowing down first and then accelerating in reverse. Friction force f=mgcos θ， Slow down first and then accelerate in reverse, with frictional force f=mgcos θ。