Are such chips possible in Google Sheets?

Question

Google Sheets

Hey!
I deal with the google sheets tool, which is new for me, several questions arose, each of which can be googled, but the questions are too strange and I don’t have enough for everything with my English. I will once again if you just answer in monosyllables with a list you can’t / you can, google this / I don’t know / etc.

1. Is it possible to set the table to be updated not every time it is opened, but only a few times a day
   
2. Is it possible to give access for a specific user to only one page (sheet)
   
3. Is it possible to give access for a certain user only to certain rows/columns
   
4. Is it possible to use today's date/current time in formulas
   

Answer 1

1.
file > spreadsheet settings > calculation > iterative calculation
2, 3: Range editing is prohibited
: protect range > set permissions
from the desired sheets to a separate document...)
4:
TODAY
NOW