I have a couple of questions concerning hosting

1. How does hosting work and why is it slow?
I've been debating with others to figure out why downloading a simple 500kb map can be very slow. Some say that it is because of the servers are too slow. Some say that the servers have nothing to do with dl speed, its all about the hosts' upload speed.

2. Is it true that when ppl are downloading in game loddy, they download from those who just downloaded?
Scenario: When you host a new map and it is full house, people will download the map while others are queued. Once the downloaders are finished, do the queued people download from others (besides the host)?

3. Does "making game public" refreshes map in the game list (besides just turning a passworded game to a public one)?
I've heard people say that when you host a map and if you keep selecting the "make game public", it will help refresh the game. Is that really true lol

4. "Too many server requests" what does that mean?
Does that mean too many ppl tried to join the hosted map at the same time and those people won't be able to join again?

1-2. Alice is the host. Bob, Cassidy, and David joins.
Alice uploads to Bob since he joined first.
Bob finishes the download; Cassidy and David starts downloading simutaneously--Alice and Bob are uploading to either of the two.

I have hosted many games with a 3.4 MB map, and they are 98% 'slow', as in the percent go up every 2-3 seconds. I had checked my bandwidth monitor and saw that my upload speed was between 5KB/s-15KB/s. For the rare 2% instances, I would upload from 15KB/s-25KB/s, but never near my ISP cap of 50KB/s. If I remember correctly, the fast speed was because of geographical closeness (try going to the Europe and Asia servers and see the upload speed). Since the Internet is all about connectivity, you should consider the Internet connection, computer speed, and location for both the uploaders and downloaders.
Also, if you played WC3, you'd know that its upload speed is much higher and that SC battle.net is very throttled.

3. The 'Make Game Public' option simply makes a passworded game unpassworded so it can be publicly seen in the games list (and buried later by newer games). If your game is already public, it does zilch. The only proven way of 'refreshing' a game for me is for someone to rejoin it. After the leaver rejoined, usually one, or a few people would then join the game again. Note that opening and closing slots never works, and I'm glad you didn't mention the egregious "F4" meme back in the 90s and early 00s.

4. The 'Too many server requests' (TMSR) has been commonplace in battle.net for years; this happens when you /stats to check a player's record, in which battle.net would either give the stats or send the error that it's busy. When players join a game, battle.net does a /stats on them automatically, and if so many joins at once, multiple requests are sent, and bnet doesn't like that; it doesn't mean players can't join again. However, if about 4-7 players immediately join in 1-2 seconds, then you'll get disconnected tempbanned from bnet.