How many people you’ve slept with.
How many times you’ve been in love.
How your sexual experiences have felt to you.
Why your past relationships have dissolved.
People you have crushes on now.
If you still have feelings for an ex.
Necessary. The person who is attempting to build intimacy with needs to know if you are not done pining for someone else. Bonus: Don’t be in a relationship with someone who still has active feelings for an ex, unless they are working to rid themselves of those feelings, rather than waiting around for that ex to come to their senses.
Cheating history.
Squirmy, but possibly necessary. Being cheated on, or cheating, can affect you in future relationships. Unless you want all that to be happening to someone who has no idea what’s going on, disclosure might be the best tack to take here.