As a Brit, maybe I can assist.
The game clock does run contiuously, yes, including through "stoppages" (injuries, substitutions). The Referee is responsible for keeping a record of how long these last for and then adding on at least that amount once the 45 or 90 minute mark is reached, along with any time considered to have been "wasted" by either team (teams ahead in the score will often slow things down to try and run down the game clock, much as a football team ahead by one score late in the game will keep the ball inbounds and use all of the 40s play clock - if the Referee considers this time wasting to be excessive, they can, and will, issue a yellow card to a player for it, but in this World Cup I think there's been a directive just to keep adding more time on; some of the early games had unusually long added time at the end of each half). The 4th official (who manages the technical/team areas) holds up the board to indicate the minimum time allowed around the end of each half (45/90).
The playing time can go on beyond that originally announced if, for example, there are additional injuries or substitutions during added time. If there is an attacking sequence of play going on, the Referee will (these days) allow it to come to a conclusion before blowing to avoid situations such as this one:
https://www.bbc.co.uk/sport/av/football/44500178 (much as in football where a play is allowed to complete even if the clock hits :00 in the middle of the play).
Think of yellow cards as UCs and red cards as flagrant UCs. Two yellows or one red and you're done for the game (and can't be replaced, so your team is down a player).
Drop kicks are still common, but usually at lower levels of play. It's a tactical decision. At the top level, most teams focus on retaining possession, so playing shorter passes from the goalkeeper to the defenders who then work the ball up the pitch is more common tactically. Drop kicks are usually considered a 50:50 chance as to which team wins the first header and which team gets the ball next after the header, so are likely to result in the other team gaining possession.
They do play with 11, but not with unlimited substitutions. It's more like football was back in the earlier parts of the last century. Limited substitutions and, once you go out, you can't come back in.
