Hi,

In Odoo the name of the CRM ie, "Customer Opportunity" is gaining by a compute method . So inorder to disable it you need to inherit the module "crm.lead" and override the field name and remove the compute function from it or you can super the compute function and change the functionality.
And to add custom sequence number in CRM please refer to our blog

https://www.cybrosys.com/blog/how-to-create-sequence-numbers-in-odoo-17#:~:text=In%20Odoo%2017%2C%20you%20can,accessing%20the%20%22Sequences%22%20option

Hope it helps

Hi,
Using automated action, you can achieve the same. See this example of generating the automatic barcode value for the product using the automated action and the sequence, using the same approach you can achieve your goal.

* Define a sequence
* Create an automated action which executes on create and get the value from sequence
* set the value to the field

Watch:  Generate Barcode For Products Using Automated Action In Odoo

Thanks