The universe is expanding. It is also expanding in a uniform manner. So although there is a geographic centre we can't possible know where it is. This is because from where we sit it looks as if everything is expanding away form us. That would make earth the centre of the universe.
This is the definition of the *observable* universe, not the universe as a whole. We cannot know that it is expanding in a uniform manner everywhere, we can only assume so. I see no reason why it cannot expand at different rates in different places - we know the speed has changed over time, so it could arguable also change locally.
And we have no idea what is outside the boundaries of the observable universe, except that we can assume that "it is more of the same", or it is not.
The universe, as it is, is being pulled from all directions (isotropic gravity or universal gravity). The expansion rate of the universe can be measured and currently is perceived to be accelerating.
This I agree with. The expansion rate seems to be accelerating, and it has apparently done so for at least several billion years. Prior to that it apparently was slowing down, according to research published by (among others) Paul Davies et al.
IF we say that the geometric point in the middle of the universe is static then the galaxies at the furthest regions of the universe are moving much faster than the closest galaxies. You can try this with a piece of elastic. ... So galaxies can and do move at the speed of light.
But see, I disagree that the universe has a center. So nothing is moving "away". From any point in the universe, everything else will appear to move away from you, and what is at the furthest point away from you will appear to move faster, even if it really isn't.
So IMHO the real illusion here is that something with mass appears to be moving at the speed of light. They are not moving like that - they only have local velocities, the perceived velocity is due to the expansion of spacetime.
This is examplified by drawing dots on the surface of a balloon. Blow some air into the balloon so it expands, and the dots will move away from each other. Yet they are not moving away from a center, and they all stand still compared to their local space.
Like the surface of the balloon, our universe is not a sphere. It only appears to be because we assume the observable universe = the universe.