So, we have 3 points...
1) can the center be hit at the time of the snap.... yes and no...
From the UIL sixman exceptions...
(9-1-14) 18. When a team is in an offensive or scrimmage kick formation, and no player is in position to take a hand to hand snap, a defensive player may not initiate contact with the snapper until one second has elapsed after the snap.
So, if the QB is under center, yes, but if the QB is in a shotgun / punt formation then no, not until one second has elapsed..
2) the guard fires off the line chops the defensive lineman.
Semantics in this game is a big part of how we as officials discuss plays and due to definitions in the rule book this can cause confusion between coaches and officials (yeah we need more confusion).
To an official, a "chop" is a high low combination block.... you, I believe, are referring to a cut block, or simply a block below the waist. If you tell an official that "they are chopping us" official says OK, I'll watch... then all he sees is low blocks... that is perfectly legal (read the last post in this
thread.
3) the center drives his man over the other two players the ref called a hi lo personal foul is this a correct call?
Technically, no... however, if the official only saw part of the play it definitely could be called. So if the official sees the block late, all he is going to see is a guy low, and a guy high on a defender, and you can certainly see how he can make the mistake and call a chop block, because we are taught to err on the side of safety, but we are also taught to see the whole play.