rules at http://dreamup.discovergreece.com/termsdu_en.pdf

1x entry. Strangely enough, the rules do not specify country eligibility, but do specify Facebook membership:

ELIGIBILITY
I. In order to participate in the Competition, users must either possess a real social media (Facebook) account or agree to enter their personal information (name, e-mail address). Fake social media Accounts will be disqualified.
II. Entry is strictly limited to one entry per person. Entries from agents or third parties are invalid.
III. The entry period for the Competition begins on Wednesday, 17.02.2016, at 00.00 GMT+2 and ends on Thursday, 31.03.2016, at 23.59 GMT+2 (the “Entry Period”). Entries performed before the commencement or after the expiration of the Entry Period are void.
IV. Eligible entrants are individuals over the age of 18 years. The entrance to the Competition requires the unreserved acceptance of the present Terms and Conditions, as well as any other terms provided by any other webpage to be utilized for the Competition purposes, which are binding in all respects for all potential participants.
V. Employees and directors (and their spouses, immediate families and household members) of the Company and its respective divisions, affiliates, agencies and subsidiaries, as well as anyone else connected in any way with the Competition or helping to set it up are not eligible to participate in the Competition or to win any prize.
VI. The Company reserves the right to verify the eligibility of all entrants and disqualify any entrant if it has reasonable grounds to believe that they have breached any of these terms and conditions.