My question is regarding the dividends of a stock. A). Dividend payout - Let’s say stock A has a dividend period twice a year; usually is this payout fixed or usually they will announce?

They will pre announce

Generally companies will aim to keep their dividend payouts higher than the previous year (ie uptrend) to install shareholder confidence. This is usually announced some time before the ex-dividend date (around a month or so but depends on the company). But of course, sometimes, such as during covid, dividends will be cut as the financial performance of the company is unable to support the dividend.