From the official Shopify Help Center: Shopify Help Center – Your Account

Check Shopify system status and troubleshoot browser settings.

Some stores still support switching account types.

Yes, through checkout and branding settings.

Modern Shopify-managed login experiences.

Older Shopify customer account experiences.

An account customers use to log into ecommerce stores.

Shared logins reduce accountability and increase security risks.

It is not recommended for security reasons.

Yes, clearing cache can solve login problems.