Hi,
1) there should be these tables:
#_contentbuilder_articles
#_contentbuilder_elements
#_contentbuilder_forms
#_contentbuilder_list_records
#_contentbuilder_list_states
#_contentbuilder_rating_cache
#_contentbuilder_records
#_contentbuilder_registered_users
#_contentbuilder_resource_access
#_contentbuilder_storages
#_contentbuilder_storage_fields
#_contentbuilder_users
#_contentbuilder_verifications
What I had in mind was to export my ContentBuilder DB so you can import it to your site. Afterwards you should be able to install the CB ( this was the fix for previous user ).
2) This is because the maximum length of a utf8mb4 character is four bytes. For a utf8 character it would be three bytes resulting in max index prefix length of 254.
One option you have is to just place lower limit on your VARCHAR fields.
Hope this helps
Regards,
Tihana