GST- ITC Refund under Zero Rated supplies without payment of tax, and such goods procured @0.1% under NN 40/2017 dated 23-10-2017. - Goods and Services Tax - GST

I kindly request all the respected experts associated with the Tax management, and all the fellow members, please reply to the querry on factual basis, it will help me and my clients immensely. I am an CA Article assistant under a mid size firm, and I have a client (ref as company) whose business is of exporting goods. The company is an star exporter under export promotion council. The company have outward supply of export without payment of tax and exempted supply within India. The Exempted supply is sale of export duty scrips which is an exempt supply under GST, and as for the ITC, the company is not liable to reverse any ITC for making such supply as per Explanation 1(d) of Rule 43 . The Export of Goods is of Goods procured under NN 40/2017 CTR , i,e. procurred on paying 0.1% of GST and the company fulfills all the condition under the said notification. The Company has made the export of Goods in April,2023. As per Section 54(1) , the Refund application can be filed within 2 years from relevant date. As per Explanation 2 (a) (ii) to section 54 relevant date is the date on which the goods passes the frontier. What is the date of passing the frontier? which document will provide such date? Is it the date of export general manifesto (E.G.M.)? Since EGM evidence that the goods have left the custom barrier and have been exported. Without EGM it is not certain that goods have left India, shipping bill can not prove such. As per Rule 84(4B) of CGST, 2017 , ' Where the person claiming refund of unutilized input tax credit on account of zero rated supplies without payment of tax has received supplies on which the supplier has availed the benefit of the Government of India, Ministry of Finance, notification No. 40/2017-Central Tax (Rate), dated the 23rd October, 2017 ,he refund of input tax credit, availed in respect of inputs received under the said notifications for export of goods and the input tax credit availed in respect of other inputs or input services to the extent used in making such export of goods, shall be granted.' As per above quoted rule, the company is allowed for such refund, and since the case is of concessional rate, refund application has to be filed under Any other category, and this type can not cross the threshold of a month. In my case, I have filed the refund application, for period April, 2023, since the export is made in April, 2023. As the rule state that the Input and Input services to the extent used in making such export shall be granted as refund. The rule does not provide a definitive clause, i.e. time limit for such expenses. The company is incurring the expenses since April, 2022 to make possible such export, therefore in the refund application, in Annexure-B (Invoice wise of ITC in accordance with GSTR-3B ) I have demanded the ITC to be refunded since April 2022 to April 2023. All the ITC is availed have been Auto Populated in GSTR-2B in their respective month. Am I in Right here??, Since the Act and Rules do not provide a definitive period of such expenses to extent to make such export. Is there any precedent set by the higher courts in this regards?? and How can one proof that expenses are in relation to such export?