D is indicted for agg assault with deadly weapon (knife). He is properly arraigned, and pleads no contest. Judge accepts plea and sets PSI. On date for sentencing D claims his name is wrong on the indictment, (idem sonans probably does not apply, but the names are related) judge dismisses case.

1) Has jeopardy attached?
2) Can state appeal?
3) Can D be reindicted? (Assuming no jeopardy)

There was no reason to dismiss. Defendant's name is as stated in indictment unless he states otherwise. And, if he states otherwise, it is simply changed. There is a separate statute for name of the defendant v. name of the victim.

Check out Wynn v. State, 8654 S.W.2d 539 (Tex. Crim. App. 1993) and see page 14, The Perfect Plea.

By what authority can a judge dismiss a case without the prosecutor's request?

In a plea agreement, double jeopardy does not attach until the judge approves the agreement (not when the judge accepts the plea). Ortiz v. State, 933 SW2d 102 (Tex. Crim. App. 1996).

If the person who appeared was not the person indicted, then no jeopardy attached as to the true defendant and the correct person needs to be arrested (and a new indictment returned, since the interloper succeeded in getting it dismissed). But, presumably the grand jury did intend to have the guy who appeared prosecuted; his name was just quite wrongly stated therein. But, at the arraignment his identity (as the person named in the indictment) was "fixed", so maybe jeopardy did attach (although he later succeeded in "unfixing" the spelling of his name) and getting the prosecution dismissed as though the indictment contained a substantive defect. The indictment was probably not void under Cook, 902 S.W.2d 471, since a person was named. See especially fn. 5. The indictment failed to meet the requirement of 21.07 and 21.02 (4), which is quite likely a defect that was waived by the defendant's failure to raise it "before the date on which the trial commenced" as required by 1.14(b). See also 26.07. I would argue the order of dismissal is void (since the court had no authority to dismiss for this defect at the time it did so). But, I am not very comfortable with the idea jeopardy never attached to the guy who appeared as the defendant.

CCP Art. 26.07 and Art. 26.09 place the burdern on the defendant to correct his name at arraignment. If he does not, he cannot thereafter use a "wrong name" defense.

Look at CCP 1.14(b)also - since it sounded like this was done at sentencing, he has waived any defects when he entered his plea.

To answer your questions more directly, in my opinion: jeopardy may have attached and therefore the State should appeal under 44.01(a)(1); which appeal should be successful because the claimed defect in the indictment was no longer a defect at the time it was brought to the attention of the court due to art. 1.14(b)and in any event, the court should not quash an indictment for this type of defect. See Mungia, 119 S.W.3d at 817: "the dismissal of an indictment is 'a drastic measure only to be used in the most extraordinary circumstances.'" On the jeopardy issue, you might also want to consider 28.05.