You can move up to your movement per round - if that is move 2 metres per CA or move them all on the same, it doesn't matter.
If he chooses to sprint, he then can do nothing else that turn (if in a precarious situation, you may want to move the character a bit each SR, so he doesn't end up near the nasty big guy prematurely).
So:
Grimolde said:
If he can sprint Move 8 x5 per Combat Round, how far could he sprint on 1 CA?
Sprint takes up all your CAs on that combar round, so it is not possible to sprint on only 1 CA.
Grimolde said:
If he 'sprints' can he then act later in the same Comat Round?
No.
Remember that even though your character does some stuff on different CA's, in real-time they would be happening at almost the same time. So, character A draws a sword, moves 5 metres and jumps over a bench. On the next turn he charges an enemy B - A is actually drawing the sword while he's running, and in one fluid movement he jumps the fallen bench and slashes at B.
Also remember that the movement system is a bit more abstract than you are used to from perhaps D&D or other systems. This is because you cannot reflect the flexibility of a real-world combat (circling combatants, dodging and small retreats) in such simple terms as D&D uses. There are many situations where you will have to remember that the miniatures on the battle map, does not reflect exact positions when fighting.
An example is when engagement reach comes into play, with nearby people who are not engaged. If character B tries to open the distance to use his spear correctly, what is the precise effect of movement on the battle grid? If A counters (opposed evade check), doesn't this mean that he also needs to be moved a bit on the grid.
The result is, you have a very expressive and detailed system, which for many reenactors feel right, and which expressed the inhering chaos and flexibility in a fight (two combatans simply do not stand in each of their own 1-metre squares, hacking at each other - they are constantly moving, even if only slightly for some combat styles). But it also means that you have to use your imagination and common sense a bit more.
Sorry for the long reply, I realise it gave a bit more than you asked for - but hopefully it helped.
- Dan