Your answer 'b' to 1 is correct. It is because there is nothing about going in the question. Use been to describe completed visits. If you have visited a place on holiday and then returned you have been there. If someone visits a place but has not come home they have gone there. so for 2 both 'a' is the correct choice by you. In 3, you cannot use 'an' with 'variant' because an is followed by a word starting with a vowel or an alphabet sounding like a vowel. In my humble view the correct form should be "n my view the variant 'a' is right.