The following script will give you a list of last updated indexes on tables which you can use to get the last updated tables.
t.name AS Table_Name
,i.name AS Index_Name
,i.type_desc AS Index_Type
,STATS_DATE(i.object_id,i.index_id) AS Date_Updated
sys.indexes i JOIN
sys.tables t ON t.object_id = i.object_id JOIN
sys.partitions sp ON i.object_id = sp.object_id
and i.index_id = sp.index_id
i.type > 0 and
sp.rows > 0
The backup you will have to do yourself as the sql backup process does not support tables backup but full database backup.