Table variable error: Must declare the scalar variable "@temp"

Either use an Allias in the table like T and use T.ID, or use just the column name.

declare @TEMP table (ID int, Name varchar(max))
insert into @temp SELECT ID, Name FROM Table

SELECT * FROM @TEMP 
WHERE ID  = 1 

A table alias cannot start with a @. So, give @Temp another alias (or leave out the two-part naming altogether):

SELECT *
FROM @TEMP t
WHERE t.ID = 1;

Also, a single equals sign is traditionally used in SQL for a comparison.