No. Shared mailboxes don’t have login credentials, so they are only accessible by licensed users who have been granted delegate access (full mailbox permission, send as, or send on behalf of). Note that Exchange Online Kiosk users don’t have delegate access, so they cannot access shared mailboxes.
Shared mailboxes have a smaller quota than regular mailboxes (10 GB), and do not include a personal archive or legal hold capabilities. If you need these features, then you can purchase either Exchange Online Plan 1 or Plan 2 and assign it to the shared mailbox.
There is no limit to the number of shared mailboxes.