All your answers will be compared to what they have in their database about you. The only winning answer is the true one. They already know most of the answers. They ask mostly to catch you lying, although sometimes this uncovers things they did not know.
Have you been issued with a UK visa in the past 10 years?
I had a standard visitor visa issues 2 years back...
Well, that answers that.
Have you been to the UK in the past 10 years?
...where I visited UK for 5 days.
There 'ya go.
How many times have you been to the UK in the past 10 years?
You'll have to answer that one yourself. It is totally correct to say "I am not sure, but I think X" . This is far better than guessing and being wrong; they view that as deception. A perfectly reasonable reason to not know is if you had 3 visits somewhere between 8 and 12 years prior, and you just don't remember which ones fell in the 10 year window.
Select why you were in the UK:
Hopefully that is straightforward, as it sounds like a pick list.
Have you applied for leave to remain in the UK in the past 10 years?
If this applied to you, you'd know it. It means you already had permission (leave) for an extended non-tourist stay, and while you were in the UK you made an application leave to remain: to stay even longer or permanently. Generally this is done by aliens who are legal residents who wish to make the situation permanent (and probably apply for citizenship).