You can't make a suit that uses magnetism to simulate gravity. Gravity acts on all matter, magnetism only acts on some materials. You could get someone to stick to a surface, but it wouldn't feel like gravity.
You could use magnetic boots/suit to 'stand' on the ceiling here on earth, but you'd still feel gravity pulling on you in its normal direction.
Linear acceleration is feasible. You can't reach the speed of light (see Relativity). You could get ever closer to it, but relativistic effects wouldn't even apply on shorter journeys (on longer ones they would, but we're a long, long way from interstellar trips). The fuel requirements are the problem.
Rotation is feasible, we just don't have the engineering or budget at the moment for ships/stations that are large enough to have a decent spin