1) There's no such thing as a hand ball. What?!? you ask. The rule is that a player (other than the keeper) can not INTENTIONALLY handle the ball with their hands, arms or with anything acting as an extension of them (shoe or shinguard). Nor can they place their arms and hands in an unnatural playing position that impedes the flight or movement of the ball, unless, as determined by the referee, that player was acting to defend themselves from injury. Think, did they hit the ball or did the ball hit them?
2) There's no rule that says a player can't play the ball while they are on the ground. However, if the downed player puts themselves or others in a position that the referee determines to be dangerous (such as falling on a ball that everyone is trying to kick) then they can signal dangerous play and award an indirect free kick to the opposing team.
3) Being in an offside position isn't necessarily offside. Offside should only be called by the referee when a player in an offside position becomes involved in play or directly benefits or interferes with play from being there. So if Suzie is off picking dandelions 40 yards offside and play heads down the field to her end, if she stays with the flowers and doesn't chase over to touch the ball, then there is no offside. However, if Suzie is picking flowers in the penalty area of the opposing goal and someone shoots and the ball bounces off the keeper or goalpost and Suzie drops her flowers to shoot on goal, then offside should be called.
4) Offside is determined when the ball is kicked. Example. Joy is jogging back after taking a shot that the keeper grabbed and punted to the other side of the field. Her teammate trapped it and sent a long ball back in towards the forwards. At the time the defender cleared the ball Joy was 10 yards offside, however, Joy is very fast and was the first to get to the ball at midfield arriving ahead of the opposing defenders and now many yards onsides. The referee blows the whistle to indicate Joy is offside and all the parents and coach erupt because she is clearly on her goal side of 3 defenders and what is the ref talking about. At the time the ball was kicked Joy was in an offside position.
5) The lines are inbounds. In soccer the lines are part of the field and part of the area that they mark. This means that for a ball to be "out of play" on the sideline or goal line, it must completely leave the field of play and no longer be touching a line or a part of the ball hanging over the line.
6) Adding time to the game. The referee is the official timekeeper. It is at the discretion of the referee to add time for injuries, time wasting, excessive ball retrieval time, etc.
7) Final pointer, in youth soccer, substitutions are mainly offered to the team in possession during throw-ins and injuries and to either team on goal kicks and starts/restarts from the center field mark. However, additional substitutions can be at the discretion of the referee, such as when the substitution is expected to take less time than the retrieval of the game ball or for the well being of a player.