People have personal preferences on what they consider acceptable length for alt text, but there's no definitive character limit or formula for how long alt text should be. That said, aim to be as detailed as needed but as succinct as possible. Go for both accuracy and precision.
Instructions for forms should appear at the beginning of the form. Some users may not notice instructions if they appear at the end of the form. If a form field requires data in a certain format (for instance, a date field that requires “day/month/year"), provide examples.
Headings serve as landmarks for users and help them understand how different pieces of information relate to each other. For example, a section with a level 3 headings probably provides information in support of information provided in the previous level 2 heading, and so on.
Automatic captions make it difficult to watch videos because the viewer is forced to decipher misspelled or mistranslated words that appear in a string of text without any punctuation. These can be distracting and disorienting. Always edit your captions before publishing.