I would give you somewhat lengthy reply instead of giving pointwise reply for your understanding. As the interim order has been passed by the ACJM in DV case u/s. 23 (2) of DV Act, you go through the particular provision, which says:
23. Power to grant interim and ex parte orders.—(1) In any proceeding before him under this Act, the Magistrate may pass such interim order as he deems just and proper.
(2) If the Magistrate is satisfied that an application prima facie discloses that the respondent is committing, or has committed an act of domestic violence or that there is a likelihood that the respondent may commit an act of domestic violence, he may grant an ex parte order on the basis of the affidavit in such form, as may be prescribed, of the aggrieved person under Section 18, Section 19, Section 20, Section 21 or, as the case may be, Section 22 against the respondent.
By bare reading of the above provision, you can understand that the court has got the power to order ex-parte under Section 20, i.e., maintenance order. As such, if the court has passed interim order without issuing notice to you, that is legal. But it is not that you do not have any relief against such ex-parte order. Read Section 25 (2) of the Act.:
(2) If the Magistrate, on receipt of an application from the aggrieved person or the respondent, is satisfied that there is a change in the circumstances requiring alteration, modification or revocation of any order made under this Act, he may, for reasons to be recorded in writing pass such order, as he may deem appropriate.
Under this section, you can move the application showing the change of circumstances for revocation of the interim maintenance order. You can further argue that her application does not disclose the true facts and obtained ex-parte order without giving you the opportunity to put your case. Alternatively, you have got one other forum to get the redressal: That is to file an appeal before the Adddl. Sessions Judge under Section 29 of the Act.
Next as per the Act, every order including the interim ex-parte order has to be given free of cost to the parties as per Section 24 of the Act.
Now, coming to your specific queries:
1. Ex-parte orders can be passed without serving notice to the respondents under this Act.
2. Further proceedings shall be held only after proper notice is served on the respondent. If you see that the court is manipulated about the receipt of court notice to you, you should move application before the court explaining how the manipulation has happened. Do not involve the judge in such murky affair. But first make sure such foul play has happened. If there was connivance between the opposite party/her counsel and the court staff, the court will take remedial action. Show those court notices and court orders in respect of service to your advocate and he can objectively assess whether such foul play has really happened or it is a figment of your imagination.
3. Maintenance order can be executable immediately after passing of the order. So, if you see any illegality in such maintenance order, you challenge it as said above in appeal u/s. 29 of the Act.