At the beginning of your upkeep...

[Nantuko Rice]

Happened during a extended playtesting with buddies:

I have "Ichorid A" in my graveyard and a Pyschatog.

At the beginning of my upkeep...
(1) I put "Ichorid A" on the stack
(2) I also discard "Ichorid B" during the beginning of my upkeep
(3) Is it still considered at the beginning of my upkeep so I can put "Ichorid B" on the stack too?

I told him it was too late, and he should've discard "Ichorid B" sooner. But he wanted to do it this turn to give tog +1/+1 of course. Thanks.

[49 Cents]

That isn't possible. Beginning of upkeep ins't a phase, it's a trigger. So the triggers have already occurred, so you're right.

[Dante]

That isn't possible. Beginning of upkeep ins't a phase, it's a trigger. So the triggers have already occurred, so you're right.

Just to clarify further on what 49 cents said, here's the relevant rules sections:

303. Upkeep Step

303.1. As the upkeep step begins, any abilities that trigger at the beginning of that upkeep step and any abilities that triggered during the turn’s untap step go on the stack. (See rule 410, “Handling Triggered Abilities.�) Then the active player gets priority and players may play spells and abilities.

410.2. Whenever a game event or game state matches a triggered ability’s trigger event, that ability triggers. When a phase or step begins, all abilities that trigger “at the beginning of� that phase or step trigger. The ability doesn’t do anything when it triggers but automatically puts the ability on the stack as soon as a player would receive priority. The ability is controlled by the player who controlled its source at the time it triggered. It has the text of the ability that created it, and no other characteristics.

So by the time either player has priority (i.e. to discard using Tog), the "beginning of upkeep" triggered abilities are already on the stack (meaning more can't go on because "beginning of upkeep" has passed).

[Nantuko Rice]

can spells or abilities be used during the untap step?

for instance, can a player discard ichorid to tog (to give it +1/+1) during the untap step and then bring back the discarded ichorid at the beginning of the upkeep?

[Matt]

No. No player has priority until the upkeep step, AFTER all "At the beginning of your/each player's upkeep" triggered abilities are on the stack (in APNAP order). Only then does the active player get priority, and he or she needs that to play abilities such as Psychatog's.