For contact Query in GST

It's absolutely fine. It's a common practice. The Tax Practitioners usually give their mobile number and e-mail address while applying for GST Registration for their convenience.

After the Registration is granted, you can amend your clients GST Registration and update his mobile number and e-mail id.

Regards,
Shivam RC.

There is no problem doing so, as almost every professional does it .

Propritor of firm used the stock worth fifty thousand for his personal use this is not sale what is the method to show in stock register