You would say "his or her". In writing, you could write "his/her". For example: A person who is only interested in his/her own troubles is not your friend.

As far as I know, they are the same. They can be used interchangeably. Unless somebody else knows better ... ?

It means "I have all four names", "I have possession of all four names", or "I know all four of the names". Same thing. He has the 4 names, but that is all he will tell us. He is implying that he is "working on" the situation, I suppose.

It is used as a "filler". It doesn't usually mean anything. It's just something to say while the person thinks of the next words. You will also hear "like" a lot. "Oh that movie? It's was kind of like ... you know ... boring ..." Other similar phrases are: ya know, ya know what I mean?, ummm, uhhhh, look, it's kinda like, sort of, yeah nah. (They all mean NOTHING) :)

Rumor is unconfirmed or unverified information. For example, "I heard that the factory is going to close down at the end of the year!" That is a rumor. Gossip is similar, but it is usually "secret" stuff about somebody else. For instance, a co-worker whispering, "Did you know Jane is pregnant?" That's gossip. Sometimes the two words can be used interchangeably; there is some overlap in their meanings. However, generally speaking, a "rumor" is nothing to be ashamed of; it's just unconfirmed information. "Gossip" is usually about a person(s) in particular, and causes embarrassment if that person(s) finds out that somebody was spreading the gossip.