Date of allotment to subscribers will be the date of incorporation of the company and the same date will also be used for printing on share certificate to be issued to subscribers. Practically & legally this is very much possible. To conclude you may use Date of Incorporation of the company for the purpose of:
1. Printing on share certificate of subscribers
2. as the date of Allotment to subscribers
3. For the purpose of filling the column in a register of a member to enter the name of subscribers.
Even if you receive the amount from subscribers after 6 months the date of deemed Allotment and date on share certificate would remain the same i.e. date of incorporation of the company.
Yes, it is valid although the registrar issued the certification on 24th on the certificate 22nd, August is written. So in the eyes of law, the company was registered on 22nd August as the certificate of incorporation is the conclusive evidence of its legal existence of the company.