Do smth for fear that... / do smth out of the fear that Hi! What’s the difference between these two?

Undoubted vs undoubtable Hi! I assume these two words do exist, but what’s the difference between them?

We had been used to standing by each other before they moved. Is it possible to use Past Perfect with ‘used to’ ?

Would you mind if I present simple/past simple? Would you mind if I go/went there with you?

Which for people? According to Virginia Evans, FCE use of English, ‘which is used for people, animals or things, alone or before nouns, one/ones or of. Can you please give a few examples when we can use which with people? Thanks.

The roses have been out for a few days. What does ‘to be out’ mean here? Outside or they are blossoming ?

What is better to use here: present perfect or present perfect continuous : He studies seriously. He has studied/been studying here for six months and he still hasn’t been going / gone to a single party.

Future continuous for actions in the present. I’ve found a rule in the book that says we can use future continuous for logical assumptions in the present. For example, I’ve called him several times but he won’t pick up his phone. Try once more. He will be sleeping. Is it common in spoken English ? What’s the difference between present continuous in such cases, like, he is sleeping now.