Yes, Samsung Metro XL does have call conference facility.
You can store up to 1000 contacts in Metro XL. In addition, you can store up to 250 contacts in each of your sim card. So, if you are using 2 sim cards, in total you can store up to 1500 contacts.
Yes, this phone supports the Nepali language.
Yes, you can adjust brightness levels as per your rquirements.
Yes, Charger is included in the standard packing.