Help With My Excel Database

The following is what I need help with:

(1) I have a main sheet where I am entering my data.

I have defined a dynamic range for this data so that if I enter a new row or
column in the sheet then this data will be included in the dynamic range.

I want to know what I need to do to copy the data from the main sheet into a
second sheet so that when I enter a new row/column or amend the existing data
in the first sheet then the second sheet will automatically update.

I presume it is something to do with referencing the dynamic range from the
first sheet into the second sheet.

Once this part has been implemented then I will lock the second sheet so
that it cannot be amended and only the first sheet can be amended.

(2) I have been using the count functions to total up data from the first
sheet into a summary sheet, for example, the total number of people from a
specific area.

I have also used SUMPRODUCT to total up dates in specific range, for
example, the total number of people born between 1.1.1970 and 31.12.1970.

I want to implement a formula in my summary sheet which will take my dynamic
range from the first sheet and search it by 2 or more conditions, for
example, I want to total up the number of people from a specific area who
were born between 1.1.1970 and 31.12.1970.

Any help would be appreciated.

Kind Regards

Roopesh