Exports under GST

Doubt in Exports under GST

Case I
if compnay submits LUT, no need to pay IGST on outward suplies of exports.
entire unutilised ITC shall be eligible for refund

Case II
if company does not submits LUT, company must pay IGST on exports of outward supplies made.
e.g. ITC availabile - 8
IGST payble on outward supplies - 10
so company need pay '2' (10-8) as IGST

My doubt is, whether entire IGST (10 in e.g.) will be refunded or only tax paid (i.e.2) will be refunded ?

If LUT is not submitted, whether Company collects the tax from recepient or they pay on inclusive basis from amount collected from sale?