A solid axle is a nonindependent suspension because the wheels on both sides of the axle are connected together.

Answer 1

That is true. Without a joint at the axle connecting to the wheel, all motion in the wheel's "plane" would be transferred to the opposite end (the other wheel). So you can think of it like the rear axle of an older pickup truck, like a "1997 Chevy S10"

Independent suspensions are common for providing greater driving comfort and greater control of the wheel's contact with the ground. Common designs are the "Double-Wishbone", "MacPherson Strut" and "Multi-link" suspensions.