This....

Candidates that assume they got the job from the first screen. Sometimes recruiters reach out to offer candidate a job opportunity; an open invitation to apply for the role or it could be an exploratory call to share more about the company but it doesn't mean you're hired (yet).
Common questions are " Who will report to me WHEN I join?" "Can I have a free parking WHEN I join" "I want a sign on bonus because..."

not uncommon at all 

Want to ask, do you normally sign the offer letter with another company before you tender or after you tender?

And let’s say after you sign the offer and your current company counter offers you, how does it work since you already signed the offer with the other company ?