hi bhebhe
here are my answers:
1. the main site you want to check is this: Marriage with a foreign citizen - Skatteetaten.no.. since your Norwegian bf is marrying you - a foreigner.. you will find all the documents and steps you need for getting married here in Norway... a valid stay is necessary to be able to get married here so you have to get married while your visa is still valid (you're still allowed to stay in Norway)...
2. yes, your sister can process DFA authentication on your behalf:
In addition, regardless of affinity, an applicant may send an authorized representative to apply on his behalf. Authorized Representative must have a valid ID and has to present a signed authorization letter or SPA from the applicant, a photocopy of applicant's ID bearing his signature, and a photocopy of the authorized representative's ID.
source link: DFA AUTHENTICATION GUIDELINES
3. I have no idea about this, i am actually unaware that DHL offers NSO/red ribbon services.. i'm sorry that i cant answer this question
4. If you have a relative in the Philippines who can process the NSO papers on your behalf, as far as I can remember, there are 2 ways you can order NSO papers (BC and CENOMAR): (1) by walk-in to the NSO office, tho i dont know if you get it right away or you need to go back after 3 days to claim it; (2) ordering online (i use ecensus.com.ph, takes 3-5 days to get delivered to your house... after acquiring the NSO document, you have to get it authenticated (or as we pinoys call it, red-ribboned)... depending on which office is closest to your sister, she have to go to the DFA office and request for the red-ribbon.. there are 2 options: (1) normal service @100 pesos, where she will have to come back after a week to claim the documents, or (2) use expedite service @200 pesos, and she can come back the next day to claim it... in my experience, i go to DFA in Macapagal (Manila) and there is a third-party mailing service booth there, where i pay an additional 150 pesos and they will take care of claiming my documents on the release date, and mail it to me.. i usually get it 2-3 days after the actual release of my documents... so from these information, try to pick what you prefer, and add to that what DHL delivery service your sister will pick to send you documents... i believe they have a rush service which allows you to receive the documents from the Philippines to Norway in 3 days, no idea how they cost tho...
furthermore, "Getting married in Norway" topic had been discussed in other threads, although we had Tourist Visas when we got married, but im pretty sure u can get other helpful information that you may need.. please try to check these forum threads:
- Marriage in Norway with Visitor's Visa (Tourist Visa)
- FAQ:Getting Married on a Tourist Visa
hope this helps