CardsplainThe fine print
has a fixed order. You draw first, and the discard comes after, so it can be any card in your hand, including the card you drew. You get the 1/1 Human Soldier only if the discarded card is not a land. What you drew plays no part.
Recruit is part of an ability, so it happens whenever that ability , even on the opponent's turn. Lake-town Lookout recruits when it , so if it dies blocking, you draw, discard and make the token in the middle of combat. Blockers are already declared by then, so that token can't block this combat.
A token that leaves the battlefield ceases to exist. A Soldier you to Stir Up Trouble is gone for good, and The Mountain-king's Return and Gathering of Darkness return creature cards only. An opposing token by Celebrate the Mountain-king never comes back, even if Celebrate leaves.
"Dies" means put into a from the battlefield. Destroy, lethal damage and sacrifice all count, so a creature sacrificed to Crude Bent Blade still triggers its "when this dies" ability. Exile is not dying. Celebrate exiles, and Gnashing of Teeth's -5/-5 mode exiles the creature if it would die that turn, so Front Porch Sentries or Lake-town Lookout get no trigger.
Check who chooses. Crude Bent Blade targets a player, and the opponent picks the creature as the ability resolves. Stir Up Trouble's sacrifice is a cost you choose and pay on casting, so it stays paid even if the spell then kills nothing.
is not a trigger. You gain the life at the same moment the damage is dealt, and the game checks life totals only after that damage is dealt, so at 2 life you survive taking 4 while your lifelink creature deals 4 at the same time.
When Celebrate leaves, the card it exiled returns as a new under its owner's control. It returns with no counters, attached to nothing, and its "enters" abilities trigger again.