What are the limitations for using shape water for cheating and forgery?
The limitations are:
Maintaining line of sight and a clear path to the water.
Having water available to manipulate and not a dry color.
Being able to somehow hide your spellcasting from those that could discern what you are doing.
Following a strict adherence to the allowed uses of the spell enumerated in its description.
Other considerations:
Your uses of shape water are imaginative, though I imagine one does not roll dice or play cards with wet surfaces.
You shape water with that spell, not evaporated colors; are your play surfaces still damp?
Spells are not necessarily subtle, unless you are using the sorcerer's Subtle Spell metamagic. This would imply there is a good chance that someone will be on to you and your cheating.
You would have to cast this spell presumably more than once to continue to manipulate the water to your liking.
It is not immediately clear that shape watercan can manipulate ice or frost; you would have to wait for it to melt or dismiss that as an Action.