It's problem-specific. Sometimes the problem IS to use certain holds only. Sometimes better sequences are found after a first ascent and a problem effectively gets redefined.
Bouldering is as much a social construct as a mathematical one, so you can't rely on any particular pattern or convention applying universally.
When using a guidebook, if no specific rules are given I assume anything goes in terms of holds.
If you prefer detailed rules then look at the limestone problems in Peak Bouldering. Every single hand and foothold numbered with the specific sequences needed for each grade. That is unusual though.
Usually, at most, you might get some rules such as don't use the arete.
One small thing that can make a difference is whether the problem is supposed to be started seated. This can make a small difference to the difficulty, or be the hardest move by miles. The abbreviation 'SDS' is sometimes used in the name to indicate a Sit-Down Start, other times it will be mentioned in the description.
Fri Night Vid Finding Focus - Life Behind The Lens of a Climbing Photographer
This week's Friday Night Video is a portrait of a prolific climbing photographer from Wedge Climbing. Sam Pratt is well known in both the outdoor and competition scene but if you haven't heard of him, you've likely seen...