2)How many times have you swum in the lake?

How long have you been swimming in the lake?

We usually use the present perfect tense to ask questions beginning with how many/much, and the present perfect continuous tense to ask questions beginning with how long.

3) I've never visited Paris.

I've already been to Paris.

always, never, yet, already and ever can't be used in a continuous tense.

4)I have not been sleeping well since I returned home.

I've been waiting for an hour.

We can use for and since with the the present perfect continuous tense.

5)Both present perfect tense and present perfect continuous tense

An action which began in the past and is still continuing or has only just finished can, with certain verbs, be expressed by either the present perfect or present perfect continuous.Verbs which can be used in this way include expect, hope, learn, lie, live, sleep, sit, study, wait, want, rain, etc.

How long have you learnt English? Or

How long have you been learning English?

It has snowed for a long time.

It has been snowing for a long time.

6 A state verb or an action verb

I have had this camera for five years.(state verb)

I have taken photos of UFOs with this camera.(action verb)

I have been taking photos of UFOs with this camera.(action verb)

An action means something happening or changing. A state means something staying the same. Some examples of action verbs are do, go, and play. Some examples of state verbs are like, know and exist.

A state verb doesn't mean an action, so it can't be used in a continuous tense.

They've always had a big garden.