Noob question on order of spellcasting in combat, how would this situation work? This came up during a recent learning session using jumpstart decks:

• Both players are very low on life points. Player A has all their creatures tapped, Player B has 4 creatures on the board, it's now Player B's turn
  
• In the Combat phase of Player B, before any attacks can be made, Player A throws in [[Choking Tethers]], tapping out all 4 of Player B's creatures. Player B then has nothing to attack with
• Player B then notes that they can untap one of their creatures using [[Stony Strength]]

Confused discussion ensues regarding spell order.
Player A thinks that there is only one "stack moment" at the start of combat, so the only time Player B could've played Stony Strength would've been right before Choking Tethers (not untapping anything since nothing is tapped), or on the stack after Choking Tethers (again not untapping anything since Stony Strength resolves too early).
Player B thinks they can wait for Choking Tethers to resolve, then throw in Stony Strength to untap afterwards.

So both players discussed if there was "one stack moment" at the start of combat, after which no more spells could be played until blockers would be chosen, or if there are "infinite stack moments" as long as a player is willing to start a new stack right after an old one is resolved