There may be no market makers
actively making markets in most or all stocks.
Market makers and specialists generally do not participate in after-hours trading, which can limit liquidity
The biggest difference between after hours and market ...
Since you didn't specify a country, this is a US centric answer:
National Best Bid and Offer (NBBO) is a Securities Exchange Commission (SEC) regulation requiring brokers to trade at the best available (lowest) ask price and the best available (highest) bid price when buying and selling securities for customers.
Any buy order at a price less than NBBO goes ...
Firstly, brokerages may have automated checks to stop this from happening. An extremely low price is a sign of a fat finger mistake, or an attempt at market manipulation.
Secondly, some stock markets forbid orders outside specific price ranges (e.g. relative to yesterday's opening/closing/high/low price). When trades breach these ranges, "circuit ...
A reduction in the dividend may signal a change in the profitability of the company. Dividends are supposed to come from retained earnings, and if the forecast by the company shows that they can't continue to afford to pay their current dividends, the reduction of the dividend amount could be the first sign of problems.
To be fair, it could also mean that ...
Many systems that allow 3rd party access to their data through an API have a way of limiting the number of calls or the amount of data accessed. They sell greater access.
This is traditionally done with an API key. To do a handful of calls requires no key, to allow X calls per hour requires you to register for API access. To make even more calls requires a ...
Anything can cause the stock price to move. The items in your list are general. The question is what happens at those events.
Do they discuss a merger, or the status of a major product line?
Do they attend an industry summit/workshop/conference where it becomes clear they are falling behind, or leading the way?
Does the booth at the trade show demonstrate ...