For arrival in the UK, it asks when did you first arrive in the UK, is this date when I entered UK and have lived non stop till now? Or do I enter the date when I arrived as a baby multiple times during visit visa

Secondly, it's asking for employment dates for the last 10 years. I only have the exact dates for my current and last employment going back 8 years. For the jobs before, I remember the months but not exact dates. Problem is that the form doesn't let me skip the dates and enter months, what shall I do?
Any help would be appreciated