You need not send the legal notice to your husband, it is not mandatory to send a legal notice before filling the petition, you can send more than 1 legal notice
You can send the legal notice under Section 9 of the Hindu Marriage Act, 1955 and you can then file a case after expiry of notice period. There is no specific time period for filling the petition after the notice, generally 15 days time is given in the notice and after that you can file.
Thus, in your matter you can send notice of section 9 Restitution of Conjugal Rights and give him atleast a minimum of 15 days time and if he does not reply to your notice within stipulated time then you have to file case under section 9 for Restitution of Conjugal Rights.
There is no time limit but you have to file the matter within a month of sending the notice. But take care that summons should be served. It may posdible that your husband will not take summons. The case will not proceed if summons is not served.
The remedy is provided in the form of Restitution of Conjugal rights. The court cannot force the party who has withdrawn from the society from the other to stay with the aggrieved person who has instituted the petition for restitution. The order or the decree is executed by the court by attaching the property of judgment debtor.
The wife can claim maintenance from the husband under Section 25 of the Hindu Marriage Act. If either of the parties doesn’t obey this decree under Section 25, then the court will attach the judgement on the debtor’s properties.
Reference: Section 9 and 25 of the Hindu Marriage Act, 1955