Question 5 is incorrect, name@example is a fully valid email address, even after RFC 2822
The spec of RFC 2822 defines an address (3.4.1) as:
local-part "@" domain
domain is defined (3.4.1) as:
domain = dot-atom / domain-literal / obs-domain
dot-atom is defined (3.2.4) as:
dot-atom = [CFWS] dot-atom-text [CFWS]
dot-atom-text = 1*atext *("." 1*atext)
1*atext meaning at least 1 alphanumeric character, followed by *("." 1*atext) meaning at least 0 "." 1*atext
If tomorrow, google decided to use its google top-level domain as an email domain, it would be perfectly valid, as could any other company owning top-level domains
Google even owns a gmail TLD so I wouldn't even be surprised if they decided to use it
It does say it's valid, but also that it's obsolete, and while the RFC does define valid but obsolete specs, there is nothing defining domains without a dot as obsolete, and it is in fact defined in the regular spec, not the obsolete section